From 1366992e16bddd5e2d9a561687f367f9f802e2e4 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sun, 10 Apr 2022 16:49:50 +0200 Subject: timekeeping: Add raw clock fallback for random_get_entropy() The addition of random_get_entropy_fallback() provides access to whichever time source has the highest frequency, which is useful for gathering entropy on platforms without available cycle counters. It's not necessarily as good as being able to quickly access a cycle counter that the CPU has, but it's still something, even when it falls back to being jiffies-based. In the event that a given arch does not define get_cycles(), falling back to the get_cycles() default implementation that returns 0 is really not the best we can do. Instead, at least calling random_get_entropy_fallback() would be preferable, because that always needs to return _something_, even falling back to jiffies eventually. It's not as though random_get_entropy_fallback() is super high precision or guaranteed to be entropic, but basically anything that's not zero all the time is better than returning zero all the time. Finally, since random_get_entropy_fallback() is used during extremely early boot when randomizing freelists in mm_init(), it can be called before timekeeping has been initialized. In that case there really is nothing we can do; jiffies hasn't even started ticking yet. So just give up and return 0. Suggested-by: Thomas Gleixner Signed-off-by: Jason A. Donenfeld Reviewed-by: Thomas Gleixner Cc: Arnd Bergmann Cc: Theodore Ts'o --- include/linux/timex.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include/linux') diff --git a/include/linux/timex.h b/include/linux/timex.h index 5745c90c8800..3871b06bd302 100644 --- a/include/linux/timex.h +++ b/include/linux/timex.h @@ -62,6 +62,8 @@ #include #include +unsigned long random_get_entropy_fallback(void); + #include #ifndef random_get_entropy @@ -74,8 +76,14 @@ * * By default we use get_cycles() for this purpose, but individual * architectures may override this in their asm/timex.h header file. + * If a given arch does not have get_cycles(), then we fallback to + * using random_get_entropy_fallback(). */ +#ifdef get_cycles #define random_get_entropy() ((unsigned long)get_cycles()) +#else +#define random_get_entropy() random_get_entropy_fallback() +#endif #endif /* -- cgit v1.2.3 From e73aaae2fa9024832e1f42e30c787c7baf61d014 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sat, 7 May 2022 14:03:46 +0200 Subject: siphash: use one source of truth for siphash permutations The SipHash family of permutations is currently used in three places: - siphash.c itself, used in the ordinary way it was intended. - random32.c, in a construction from an anonymous contributor. - random.c, as part of its fast_mix function. Each one of these places reinvents the wheel with the same C code, same rotation constants, and same symmetry-breaking constants. This commit tidies things up a bit by placing macros for the permutations and constants into siphash.h, where each of the three .c users can access them. It also leaves a note dissuading more users of them from emerging. Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 30 +++++++----------------------- include/linux/prandom.h | 23 +++++++---------------- include/linux/siphash.h | 28 ++++++++++++++++++++++++++++ lib/siphash.c | 32 ++++++++++---------------------- 4 files changed, 52 insertions(+), 61 deletions(-) (limited to 'include/linux') diff --git a/drivers/char/random.c b/drivers/char/random.c index 8be3efd65ef2..c1763bcbcaed 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -52,6 +52,7 @@ #include #include #include +#include #include #include #include @@ -1086,12 +1087,11 @@ struct fast_pool { static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = { #ifdef CONFIG_64BIT - /* SipHash constants */ - .pool = { 0x736f6d6570736575UL, 0x646f72616e646f6dUL, - 0x6c7967656e657261UL, 0x7465646279746573UL } +#define FASTMIX_PERM SIPHASH_PERMUTATION + .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 } #else - /* HalfSipHash constants */ - .pool = { 0, 0, 0x6c796765U, 0x74656462U } +#define FASTMIX_PERM HSIPHASH_PERMUTATION + .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 } #endif }; @@ -1103,27 +1103,11 @@ static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = { */ static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2) { -#ifdef CONFIG_64BIT -#define PERM() do { \ - s[0] += s[1]; s[1] = rol64(s[1], 13); s[1] ^= s[0]; s[0] = rol64(s[0], 32); \ - s[2] += s[3]; s[3] = rol64(s[3], 16); s[3] ^= s[2]; \ - s[0] += s[3]; s[3] = rol64(s[3], 21); s[3] ^= s[0]; \ - s[2] += s[1]; s[1] = rol64(s[1], 17); s[1] ^= s[2]; s[2] = rol64(s[2], 32); \ -} while (0) -#else -#define PERM() do { \ - s[0] += s[1]; s[1] = rol32(s[1], 5); s[1] ^= s[0]; s[0] = rol32(s[0], 16); \ - s[2] += s[3]; s[3] = rol32(s[3], 8); s[3] ^= s[2]; \ - s[0] += s[3]; s[3] = rol32(s[3], 7); s[3] ^= s[0]; \ - s[2] += s[1]; s[1] = rol32(s[1], 13); s[1] ^= s[2]; s[2] = rol32(s[2], 16); \ -} while (0) -#endif - s[3] ^= v1; - PERM(); + FASTMIX_PERM(s[0], s[1], s[2], s[3]); s[0] ^= v1; s[3] ^= v2; - PERM(); + FASTMIX_PERM(s[0], s[1], s[2], s[3]); s[0] ^= v2; } diff --git a/include/linux/prandom.h b/include/linux/prandom.h index 056d31317e49..a4aadd2dc153 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -10,6 +10,7 @@ #include #include +#include u32 prandom_u32(void); void prandom_bytes(void *buf, size_t nbytes); @@ -27,15 +28,10 @@ DECLARE_PER_CPU(unsigned long, net_rand_noise); * The core SipHash round function. Each line can be executed in * parallel given enough CPU resources. */ -#define PRND_SIPROUND(v0, v1, v2, v3) ( \ - v0 += v1, v1 = rol64(v1, 13), v2 += v3, v3 = rol64(v3, 16), \ - v1 ^= v0, v0 = rol64(v0, 32), v3 ^= v2, \ - v0 += v3, v3 = rol64(v3, 21), v2 += v1, v1 = rol64(v1, 17), \ - v3 ^= v0, v1 ^= v2, v2 = rol64(v2, 32) \ -) +#define PRND_SIPROUND(v0, v1, v2, v3) SIPHASH_PERMUTATION(v0, v1, v2, v3) -#define PRND_K0 (0x736f6d6570736575 ^ 0x6c7967656e657261) -#define PRND_K1 (0x646f72616e646f6d ^ 0x7465646279746573) +#define PRND_K0 (SIPHASH_CONST_0 ^ SIPHASH_CONST_2) +#define PRND_K1 (SIPHASH_CONST_1 ^ SIPHASH_CONST_3) #elif BITS_PER_LONG == 32 /* @@ -43,14 +39,9 @@ DECLARE_PER_CPU(unsigned long, net_rand_noise); * This is weaker, but 32-bit machines are not used for high-traffic * applications, so there is less output for an attacker to analyze. */ -#define PRND_SIPROUND(v0, v1, v2, v3) ( \ - v0 += v1, v1 = rol32(v1, 5), v2 += v3, v3 = rol32(v3, 8), \ - v1 ^= v0, v0 = rol32(v0, 16), v3 ^= v2, \ - v0 += v3, v3 = rol32(v3, 7), v2 += v1, v1 = rol32(v1, 13), \ - v3 ^= v0, v1 ^= v2, v2 = rol32(v2, 16) \ -) -#define PRND_K0 0x6c796765 -#define PRND_K1 0x74656462 +#define PRND_SIPROUND(v0, v1, v2, v3) HSIPHASH_PERMUTATION(v0, v1, v2, v3) +#define PRND_K0 (HSIPHASH_CONST_0 ^ HSIPHASH_CONST_2) +#define PRND_K1 (HSIPHASH_CONST_1 ^ HSIPHASH_CONST_3) #else #error Unsupported BITS_PER_LONG diff --git a/include/linux/siphash.h b/include/linux/siphash.h index cce8a9acc76c..3af1428da559 100644 --- a/include/linux/siphash.h +++ b/include/linux/siphash.h @@ -138,4 +138,32 @@ static inline u32 hsiphash(const void *data, size_t len, return ___hsiphash_aligned(data, len, key); } +/* + * These macros expose the raw SipHash and HalfSipHash permutations. + * Do not use them directly! If you think you have a use for them, + * be sure to CC the maintainer of this file explaining why. + */ + +#define SIPHASH_PERMUTATION(a, b, c, d) ( \ + (a) += (b), (b) = rol64((b), 13), (b) ^= (a), (a) = rol64((a), 32), \ + (c) += (d), (d) = rol64((d), 16), (d) ^= (c), \ + (a) += (d), (d) = rol64((d), 21), (d) ^= (a), \ + (c) += (b), (b) = rol64((b), 17), (b) ^= (c), (c) = rol64((c), 32)) + +#define SIPHASH_CONST_0 0x736f6d6570736575ULL +#define SIPHASH_CONST_1 0x646f72616e646f6dULL +#define SIPHASH_CONST_2 0x6c7967656e657261ULL +#define SIPHASH_CONST_3 0x7465646279746573ULL + +#define HSIPHASH_PERMUTATION(a, b, c, d) ( \ + (a) += (b), (b) = rol32((b), 5), (b) ^= (a), (a) = rol32((a), 16), \ + (c) += (d), (d) = rol32((d), 8), (d) ^= (c), \ + (a) += (d), (d) = rol32((d), 7), (d) ^= (a), \ + (c) += (b), (b) = rol32((b), 13), (b) ^= (c), (c) = rol32((c), 16)) + +#define HSIPHASH_CONST_0 0U +#define HSIPHASH_CONST_1 0U +#define HSIPHASH_CONST_2 0x6c796765U +#define HSIPHASH_CONST_3 0x74656462U + #endif /* _LINUX_SIPHASH_H */ diff --git a/lib/siphash.c b/lib/siphash.c index 72b9068ab57b..71d315a6ad62 100644 --- a/lib/siphash.c +++ b/lib/siphash.c @@ -18,19 +18,13 @@ #include #endif -#define SIPROUND \ - do { \ - v0 += v1; v1 = rol64(v1, 13); v1 ^= v0; v0 = rol64(v0, 32); \ - v2 += v3; v3 = rol64(v3, 16); v3 ^= v2; \ - v0 += v3; v3 = rol64(v3, 21); v3 ^= v0; \ - v2 += v1; v1 = rol64(v1, 17); v1 ^= v2; v2 = rol64(v2, 32); \ - } while (0) +#define SIPROUND SIPHASH_PERMUTATION(v0, v1, v2, v3) #define PREAMBLE(len) \ - u64 v0 = 0x736f6d6570736575ULL; \ - u64 v1 = 0x646f72616e646f6dULL; \ - u64 v2 = 0x6c7967656e657261ULL; \ - u64 v3 = 0x7465646279746573ULL; \ + u64 v0 = SIPHASH_CONST_0; \ + u64 v1 = SIPHASH_CONST_1; \ + u64 v2 = SIPHASH_CONST_2; \ + u64 v3 = SIPHASH_CONST_3; \ u64 b = ((u64)(len)) << 56; \ v3 ^= key->key[1]; \ v2 ^= key->key[0]; \ @@ -389,19 +383,13 @@ u32 hsiphash_4u32(const u32 first, const u32 second, const u32 third, } EXPORT_SYMBOL(hsiphash_4u32); #else -#define HSIPROUND \ - do { \ - v0 += v1; v1 = rol32(v1, 5); v1 ^= v0; v0 = rol32(v0, 16); \ - v2 += v3; v3 = rol32(v3, 8); v3 ^= v2; \ - v0 += v3; v3 = rol32(v3, 7); v3 ^= v0; \ - v2 += v1; v1 = rol32(v1, 13); v1 ^= v2; v2 = rol32(v2, 16); \ - } while (0) +#define HSIPROUND HSIPHASH_PERMUTATION(v0, v1, v2, v3) #define HPREAMBLE(len) \ - u32 v0 = 0; \ - u32 v1 = 0; \ - u32 v2 = 0x6c796765U; \ - u32 v3 = 0x74656462U; \ + u32 v0 = HSIPHASH_CONST_0; \ + u32 v1 = HSIPHASH_CONST_1; \ + u32 v2 = HSIPHASH_CONST_2; \ + u32 v3 = HSIPHASH_CONST_3; \ u32 b = ((u32)(len)) << 24; \ v3 ^= key->key[1]; \ v2 ^= key->key[0]; \ -- cgit v1.2.3 From d4150779e60fb6c49be25572596b2cdfc5d46a09 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 11 May 2022 16:11:29 +0200 Subject: random32: use real rng for non-deterministic randomness MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit random32.c has two random number generators in it: one that is meant to be used deterministically, with some predefined seed, and one that does the same exact thing as random.c, except does it poorly. The first one has some use cases. The second one no longer does and can be replaced with calls to random.c's proper random number generator. The relatively recent siphash-based bad random32.c code was added in response to concerns that the prior random32.c was too deterministic. Out of fears that random.c was (at the time) too slow, this code was anonymously contributed. Then out of that emerged a kind of shadow entropy gathering system, with its own tentacles throughout various net code, added willy nilly. Stop👏making👏bespoke👏random👏number👏generators👏. Fortunately, recent advances in random.c mean that we can stop playing with this sketchiness, and just use get_random_u32(), which is now fast enough. In micro benchmarks using RDPMC, I'm seeing the same median cycle count between the two functions, with the mean being _slightly_ higher due to batches refilling (which we can optimize further need be). However, when doing *real* benchmarks of the net functions that actually use these random numbers, the mean cycles actually *decreased* slightly (with the median still staying the same), likely because the additional prandom code means icache misses and complexity, whereas random.c is generally already being used by something else nearby. The biggest benefit of this is that there are many users of prandom who probably should be using cryptographically secure random numbers. This makes all of those accidental cases become secure by just flipping a switch. Later on, we can do a tree-wide cleanup to remove the static inline wrapper functions that this commit adds. There are also some low-ish hanging fruits for making this even faster in the future: a get_random_u16() function for use in the networking stack will give a 2x performance boost there, using SIMD for ChaCha20 will let us compute 4 or 8 or 16 blocks of output in parallel, instead of just one, giving us large buffers for cheap, and introducing a get_random_*_bh() function that assumes irqs are already disabled will shave off a few cycles for ordinary calls. These are things we can chip away at down the road. Acked-by: Jakub Kicinski Acked-by: Theodore Ts'o Signed-off-by: Jason A. Donenfeld --- include/linux/prandom.h | 52 +------- kernel/time/timer.c | 2 - lib/random32.c | 347 +----------------------------------------------- net/core/dev.c | 3 - net/ipv4/devinet.c | 4 +- net/ipv6/addrconf.c | 2 - 6 files changed, 15 insertions(+), 395 deletions(-) (limited to 'include/linux') diff --git a/include/linux/prandom.h b/include/linux/prandom.h index a4aadd2dc153..deace5fb4e62 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -10,53 +10,16 @@ #include #include -#include +#include -u32 prandom_u32(void); -void prandom_bytes(void *buf, size_t nbytes); -void prandom_seed(u32 seed); -void prandom_reseed_late(void); - -DECLARE_PER_CPU(unsigned long, net_rand_noise); - -#define PRANDOM_ADD_NOISE(a, b, c, d) \ - prandom_u32_add_noise((unsigned long)(a), (unsigned long)(b), \ - (unsigned long)(c), (unsigned long)(d)) - -#if BITS_PER_LONG == 64 -/* - * The core SipHash round function. Each line can be executed in - * parallel given enough CPU resources. - */ -#define PRND_SIPROUND(v0, v1, v2, v3) SIPHASH_PERMUTATION(v0, v1, v2, v3) - -#define PRND_K0 (SIPHASH_CONST_0 ^ SIPHASH_CONST_2) -#define PRND_K1 (SIPHASH_CONST_1 ^ SIPHASH_CONST_3) - -#elif BITS_PER_LONG == 32 -/* - * On 32-bit machines, we use HSipHash, a reduced-width version of SipHash. - * This is weaker, but 32-bit machines are not used for high-traffic - * applications, so there is less output for an attacker to analyze. - */ -#define PRND_SIPROUND(v0, v1, v2, v3) HSIPHASH_PERMUTATION(v0, v1, v2, v3) -#define PRND_K0 (HSIPHASH_CONST_0 ^ HSIPHASH_CONST_2) -#define PRND_K1 (HSIPHASH_CONST_1 ^ HSIPHASH_CONST_3) - -#else -#error Unsupported BITS_PER_LONG -#endif +static inline u32 prandom_u32(void) +{ + return get_random_u32(); +} -static inline void prandom_u32_add_noise(unsigned long a, unsigned long b, - unsigned long c, unsigned long d) +static inline void prandom_bytes(void *buf, size_t nbytes) { - /* - * This is not used cryptographically; it's just - * a convenient 4-word hash function. (3 xor, 2 add, 2 rol) - */ - a ^= raw_cpu_read(net_rand_noise); - PRND_SIPROUND(a, b, c, d); - raw_cpu_write(net_rand_noise, d); + return get_random_bytes(buf, nbytes); } struct rnd_state { @@ -108,7 +71,6 @@ static inline void prandom_seed_state(struct rnd_state *state, u64 seed) state->s2 = __seed(i, 8U); state->s3 = __seed(i, 16U); state->s4 = __seed(i, 128U); - PRANDOM_ADD_NOISE(state, i, 0, 0); } /* Pseudo random number generator from numerical recipes. */ diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 9dd2a39cb3b0..c12fe329c9ff 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1780,8 +1780,6 @@ void update_process_times(int user_tick) { struct task_struct *p = current; - PRANDOM_ADD_NOISE(jiffies, user_tick, p, 0); - /* Note: this timer irq context must be accounted for as well. */ account_process_tick(p, user_tick); run_local_timers(); diff --git a/lib/random32.c b/lib/random32.c index 976632003ec6..d5d9029362cb 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -245,25 +245,13 @@ static struct prandom_test2 { { 407983964U, 921U, 728767059U }, }; -static u32 __extract_hwseed(void) -{ - unsigned int val = 0; - - (void)(arch_get_random_seed_int(&val) || - arch_get_random_int(&val)); - - return val; -} - -static void prandom_seed_early(struct rnd_state *state, u32 seed, - bool mix_with_hwseed) +static void prandom_state_selftest_seed(struct rnd_state *state, u32 seed) { #define LCG(x) ((x) * 69069U) /* super-duper LCG */ -#define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0) - state->s1 = __seed(HWSEED() ^ LCG(seed), 2U); - state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U); - state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U); - state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U); + state->s1 = __seed(LCG(seed), 2U); + state->s2 = __seed(LCG(state->s1), 8U); + state->s3 = __seed(LCG(state->s2), 16U); + state->s4 = __seed(LCG(state->s3), 128U); } static int __init prandom_state_selftest(void) @@ -274,7 +262,7 @@ static int __init prandom_state_selftest(void) for (i = 0; i < ARRAY_SIZE(test1); i++) { struct rnd_state state; - prandom_seed_early(&state, test1[i].seed, false); + prandom_state_selftest_seed(&state, test1[i].seed); prandom_warmup(&state); if (test1[i].result != prandom_u32_state(&state)) @@ -289,7 +277,7 @@ static int __init prandom_state_selftest(void) for (i = 0; i < ARRAY_SIZE(test2); i++) { struct rnd_state state; - prandom_seed_early(&state, test2[i].seed, false); + prandom_state_selftest_seed(&state, test2[i].seed); prandom_warmup(&state); for (j = 0; j < test2[i].iteration - 1; j++) @@ -310,324 +298,3 @@ static int __init prandom_state_selftest(void) } core_initcall(prandom_state_selftest); #endif - -/* - * The prandom_u32() implementation is now completely separate from the - * prandom_state() functions, which are retained (for now) for compatibility. - * - * Because of (ab)use in the networking code for choosing random TCP/UDP port - * numbers, which open DoS possibilities if guessable, we want something - * stronger than a standard PRNG. But the performance requirements of - * the network code do not allow robust crypto for this application. - * - * So this is a homebrew Junior Spaceman implementation, based on the - * lowest-latency trustworthy crypto primitive available, SipHash. - * (The authors of SipHash have not been consulted about this abuse of - * their work.) - * - * Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to - * one word of output. This abbreviated version uses 2 rounds per word - * of output. - */ - -struct siprand_state { - unsigned long v0; - unsigned long v1; - unsigned long v2; - unsigned long v3; -}; - -static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy; -DEFINE_PER_CPU(unsigned long, net_rand_noise); -EXPORT_PER_CPU_SYMBOL(net_rand_noise); - -/* - * This is the core CPRNG function. As "pseudorandom", this is not used - * for truly valuable things, just intended to be a PITA to guess. - * For maximum speed, we do just two SipHash rounds per word. This is - * the same rate as 4 rounds per 64 bits that SipHash normally uses, - * so hopefully it's reasonably secure. - * - * There are two changes from the official SipHash finalization: - * - We omit some constants XORed with v2 in the SipHash spec as irrelevant; - * they are there only to make the output rounds distinct from the input - * rounds, and this application has no input rounds. - * - Rather than returning v0^v1^v2^v3, return v1+v3. - * If you look at the SipHash round, the last operation on v3 is - * "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time. - * Likewise "v1 ^= v2". (The rotate of v2 makes a difference, but - * it still cancels out half of the bits in v2 for no benefit.) - * Second, since the last combining operation was xor, continue the - * pattern of alternating xor/add for a tiny bit of extra non-linearity. - */ -static inline u32 siprand_u32(struct siprand_state *s) -{ - unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3; - unsigned long n = raw_cpu_read(net_rand_noise); - - v3 ^= n; - PRND_SIPROUND(v0, v1, v2, v3); - PRND_SIPROUND(v0, v1, v2, v3); - v0 ^= n; - s->v0 = v0; s->v1 = v1; s->v2 = v2; s->v3 = v3; - return v1 + v3; -} - - -/** - * prandom_u32 - pseudo random number generator - * - * A 32 bit pseudo-random number is generated using a fast - * algorithm suitable for simulation. This algorithm is NOT - * considered safe for cryptographic use. - */ -u32 prandom_u32(void) -{ - struct siprand_state *state = get_cpu_ptr(&net_rand_state); - u32 res = siprand_u32(state); - - put_cpu_ptr(&net_rand_state); - return res; -} -EXPORT_SYMBOL(prandom_u32); - -/** - * prandom_bytes - get the requested number of pseudo-random bytes - * @buf: where to copy the pseudo-random bytes to - * @bytes: the requested number of bytes - */ -void prandom_bytes(void *buf, size_t bytes) -{ - struct siprand_state *state = get_cpu_ptr(&net_rand_state); - u8 *ptr = buf; - - while (bytes >= sizeof(u32)) { - put_unaligned(siprand_u32(state), (u32 *)ptr); - ptr += sizeof(u32); - bytes -= sizeof(u32); - } - - if (bytes > 0) { - u32 rem = siprand_u32(state); - - do { - *ptr++ = (u8)rem; - rem >>= BITS_PER_BYTE; - } while (--bytes > 0); - } - put_cpu_ptr(&net_rand_state); -} -EXPORT_SYMBOL(prandom_bytes); - -/** - * prandom_seed - add entropy to pseudo random number generator - * @entropy: entropy value - * - * Add some additional seed material to the prandom pool. - * The "entropy" is actually our IP address (the only caller is - * the network code), not for unpredictability, but to ensure that - * different machines are initialized differently. - */ -void prandom_seed(u32 entropy) -{ - int i; - - add_device_randomness(&entropy, sizeof(entropy)); - - for_each_possible_cpu(i) { - struct siprand_state *state = per_cpu_ptr(&net_rand_state, i); - unsigned long v0 = state->v0, v1 = state->v1; - unsigned long v2 = state->v2, v3 = state->v3; - - do { - v3 ^= entropy; - PRND_SIPROUND(v0, v1, v2, v3); - PRND_SIPROUND(v0, v1, v2, v3); - v0 ^= entropy; - } while (unlikely(!v0 || !v1 || !v2 || !v3)); - - WRITE_ONCE(state->v0, v0); - WRITE_ONCE(state->v1, v1); - WRITE_ONCE(state->v2, v2); - WRITE_ONCE(state->v3, v3); - } -} -EXPORT_SYMBOL(prandom_seed); - -/* - * Generate some initially weak seeding values to allow - * the prandom_u32() engine to be started. - */ -static int __init prandom_init_early(void) -{ - int i; - unsigned long v0, v1, v2, v3; - - if (!arch_get_random_long(&v0)) - v0 = jiffies; - if (!arch_get_random_long(&v1)) - v1 = random_get_entropy(); - v2 = v0 ^ PRND_K0; - v3 = v1 ^ PRND_K1; - - for_each_possible_cpu(i) { - struct siprand_state *state; - - v3 ^= i; - PRND_SIPROUND(v0, v1, v2, v3); - PRND_SIPROUND(v0, v1, v2, v3); - v0 ^= i; - - state = per_cpu_ptr(&net_rand_state, i); - state->v0 = v0; state->v1 = v1; - state->v2 = v2; state->v3 = v3; - } - - return 0; -} -core_initcall(prandom_init_early); - - -/* Stronger reseeding when available, and periodically thereafter. */ -static void prandom_reseed(struct timer_list *unused); - -static DEFINE_TIMER(seed_timer, prandom_reseed); - -static void prandom_reseed(struct timer_list *unused) -{ - unsigned long expires; - int i; - - /* - * Reinitialize each CPU's PRNG with 128 bits of key. - * No locking on the CPUs, but then somewhat random results are, - * well, expected. - */ - for_each_possible_cpu(i) { - struct siprand_state *state; - unsigned long v0 = get_random_long(), v2 = v0 ^ PRND_K0; - unsigned long v1 = get_random_long(), v3 = v1 ^ PRND_K1; -#if BITS_PER_LONG == 32 - int j; - - /* - * On 32-bit machines, hash in two extra words to - * approximate 128-bit key length. Not that the hash - * has that much security, but this prevents a trivial - * 64-bit brute force. - */ - for (j = 0; j < 2; j++) { - unsigned long m = get_random_long(); - - v3 ^= m; - PRND_SIPROUND(v0, v1, v2, v3); - PRND_SIPROUND(v0, v1, v2, v3); - v0 ^= m; - } -#endif - /* - * Probably impossible in practice, but there is a - * theoretical risk that a race between this reseeding - * and the target CPU writing its state back could - * create the all-zero SipHash fixed point. - * - * To ensure that never happens, ensure the state - * we write contains no zero words. - */ - state = per_cpu_ptr(&net_rand_state, i); - WRITE_ONCE(state->v0, v0 ? v0 : -1ul); - WRITE_ONCE(state->v1, v1 ? v1 : -1ul); - WRITE_ONCE(state->v2, v2 ? v2 : -1ul); - WRITE_ONCE(state->v3, v3 ? v3 : -1ul); - } - - /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ - expires = round_jiffies(jiffies + 40 * HZ + prandom_u32_max(40 * HZ)); - mod_timer(&seed_timer, expires); -} - -/* - * The random ready callback can be called from almost any interrupt. - * To avoid worrying about whether it's safe to delay that interrupt - * long enough to seed all CPUs, just schedule an immediate timer event. - */ -static int prandom_timer_start(struct notifier_block *nb, - unsigned long action, void *data) -{ - mod_timer(&seed_timer, jiffies); - return 0; -} - -#ifdef CONFIG_RANDOM32_SELFTEST -/* Principle: True 32-bit random numbers will all have 16 differing bits on - * average. For each 32-bit number, there are 601M numbers differing by 16 - * bits, and 89% of the numbers differ by at least 12 bits. Note that more - * than 16 differing bits also implies a correlation with inverted bits. Thus - * we take 1024 random numbers and compare each of them to the other ones, - * counting the deviation of correlated bits to 16. Constants report 32, - * counters 32-log2(TEST_SIZE), and pure randoms, around 6 or lower. With the - * u32 total, TEST_SIZE may be as large as 4096 samples. - */ -#define TEST_SIZE 1024 -static int __init prandom32_state_selftest(void) -{ - unsigned int x, y, bits, samples; - u32 xor, flip; - u32 total; - u32 *data; - - data = kmalloc(sizeof(*data) * TEST_SIZE, GFP_KERNEL); - if (!data) - return 0; - - for (samples = 0; samples < TEST_SIZE; samples++) - data[samples] = prandom_u32(); - - flip = total = 0; - for (x = 0; x < samples; x++) { - for (y = 0; y < samples; y++) { - if (x == y) - continue; - xor = data[x] ^ data[y]; - flip |= xor; - bits = hweight32(xor); - total += (bits - 16) * (bits - 16); - } - } - - /* We'll return the average deviation as 2*sqrt(corr/samples), which - * is also sqrt(4*corr/samples) which provides a better resolution. - */ - bits = int_sqrt(total / (samples * (samples - 1)) * 4); - if (bits > 6) - pr_warn("prandom32: self test failed (at least %u bits" - " correlated, fixed_mask=%#x fixed_value=%#x\n", - bits, ~flip, data[0] & ~flip); - else - pr_info("prandom32: self test passed (less than %u bits" - " correlated)\n", - bits+1); - kfree(data); - return 0; -} -core_initcall(prandom32_state_selftest); -#endif /* CONFIG_RANDOM32_SELFTEST */ - -/* - * Start periodic full reseeding as soon as strong - * random numbers are available. - */ -static int __init prandom_init_late(void) -{ - static struct notifier_block random_ready = { - .notifier_call = prandom_timer_start - }; - int ret = register_random_ready_notifier(&random_ready); - - if (ret == -EALREADY) { - prandom_timer_start(&random_ready, 0, NULL); - ret = 0; - } - return ret; -} -late_initcall(prandom_init_late); diff --git a/net/core/dev.c b/net/core/dev.c index 1461c2d9dec8..19c9beb1136b 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3527,7 +3527,6 @@ static int xmit_one(struct sk_buff *skb, struct net_device *dev, dev_queue_xmit_nit(skb, dev); len = skb->len; - PRANDOM_ADD_NOISE(skb, dev, txq, len + jiffies); trace_net_dev_start_xmit(skb, dev); rc = netdev_start_xmit(skb, dev, txq, more); trace_net_dev_xmit(skb, rc, dev, len); @@ -4168,7 +4167,6 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev) if (!skb) goto out; - PRANDOM_ADD_NOISE(skb, dev, txq, jiffies); HARD_TX_LOCK(dev, txq, cpu); if (!netif_xmit_stopped(txq)) { @@ -4234,7 +4232,6 @@ int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id) skb_set_queue_mapping(skb, queue_id); txq = skb_get_tx_queue(dev, skb); - PRANDOM_ADD_NOISE(skb, dev, txq, jiffies); local_bh_disable(); diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index 53a6b14dc50a..3d6d33ac20cc 100644 --- a/net/ipv4/devinet.c +++ b/net/ipv4/devinet.c @@ -536,10 +536,8 @@ static int __inet_insert_ifa(struct in_ifaddr *ifa, struct nlmsghdr *nlh, return ret; } - if (!(ifa->ifa_flags & IFA_F_SECONDARY)) { - prandom_seed((__force u32) ifa->ifa_local); + if (!(ifa->ifa_flags & IFA_F_SECONDARY)) ifap = last_primary; - } rcu_assign_pointer(ifa->ifa_next, *ifap); rcu_assign_pointer(*ifap, ifa); diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index b22504176588..e7c68fa12fae 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -3972,8 +3972,6 @@ static void addrconf_dad_begin(struct inet6_ifaddr *ifp) addrconf_join_solict(dev, &ifp->addr); - prandom_seed((__force u32) ifp->addr.s6_addr32[3]); - read_lock_bh(&idev->lock); spin_lock(&ifp->lock); if (ifp->state == INET6_IFADDR_STATE_DEAD) -- cgit v1.2.3 From 2f14062bb14b0fcfcc21e6dc7d5b5c0d25966164 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Thu, 5 May 2022 02:20:22 +0200 Subject: random: handle latent entropy and command line from random_init() Currently, start_kernel() adds latent entropy and the command line to the entropy bool *after* the RNG has been initialized, deferring when it's actually used by things like stack canaries until the next time the pool is seeded. This surely is not intended. Rather than splitting up which entropy gets added where and when between start_kernel() and random_init(), just do everything in random_init(), which should eliminate these kinds of bugs in the future. While we're at it, rename the awkwardly titled "rand_initialize()" to the more standard "random_init()" nomenclature. Reviewed-by: Dominik Brodowski Signed-off-by: Jason A. Donenfeld --- arch/openrisc/kernel/head.S | 2 +- drivers/char/random.c | 17 ++++++++++------- include/linux/random.h | 15 +++++++-------- init/main.c | 10 +++------- 4 files changed, 21 insertions(+), 23 deletions(-) (limited to 'include/linux') diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S index 871f4c858859..2fa6cefa62ca 100644 --- a/arch/openrisc/kernel/head.S +++ b/arch/openrisc/kernel/head.S @@ -525,7 +525,7 @@ _start: * Start the TTCR as early as possible, so that the RNG can make use of * measurements of boot time from the earliest opportunity. Especially * important is that the TTCR does not return zero by the time we reach - * rand_initialize(). + * random_init(). */ l.movhi r3,hi(SPR_TTMR_CR) l.mtspr r0,r3,SPR_TTMR diff --git a/drivers/char/random.c b/drivers/char/random.c index 9024aeba2d28..95982dc08669 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -919,12 +919,13 @@ static struct notifier_block pm_notifier = { .notifier_call = random_pm_notifica /* * The first collection of entropy occurs at system boot while interrupts - * are still turned off. Here we push in RDSEED, a timestamp, and utsname(). - * Depending on the above configuration knob, RDSEED may be considered - * sufficient for initialization. Note that much earlier setup may already - * have pushed entropy into the input pool by the time we get here. + * are still turned off. Here we push in latent entropy, RDSEED, a timestamp, + * utsname(), and the command line. Depending on the above configuration knob, + * RDSEED may be considered sufficient for initialization. Note that much + * earlier setup may already have pushed entropy into the input pool by the + * time we get here. */ -int __init rand_initialize(void) +int __init random_init(const char *command_line) { size_t i; ktime_t now = ktime_get_real(); @@ -946,6 +947,8 @@ int __init rand_initialize(void) } _mix_pool_bytes(&now, sizeof(now)); _mix_pool_bytes(utsname(), sizeof(*(utsname()))); + _mix_pool_bytes(command_line, strlen(command_line)); + add_latent_entropy(); if (crng_ready()) crng_reseed(); @@ -1685,8 +1688,8 @@ static struct ctl_table random_table[] = { }; /* - * rand_initialize() is called before sysctl_init(), - * so we cannot call register_sysctl_init() in rand_initialize() + * random_init() is called before sysctl_init(), + * so we cannot call register_sysctl_init() in random_init() */ static int __init random_sysctls_init(void) { diff --git a/include/linux/random.h b/include/linux/random.h index f673fbb838b3..b52963955a99 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -14,22 +14,21 @@ struct notifier_block; extern void add_device_randomness(const void *, size_t); extern void add_bootloader_randomness(const void *, size_t); +extern void add_input_randomness(unsigned int type, unsigned int code, + unsigned int value) __latent_entropy; +extern void add_interrupt_randomness(int irq) __latent_entropy; +extern void add_hwgenerator_randomness(const void *buffer, size_t count, + size_t entropy); #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) static inline void add_latent_entropy(void) { - add_device_randomness((const void *)&latent_entropy, - sizeof(latent_entropy)); + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); } #else static inline void add_latent_entropy(void) {} #endif -extern void add_input_randomness(unsigned int type, unsigned int code, - unsigned int value) __latent_entropy; -extern void add_interrupt_randomness(int irq) __latent_entropy; -extern void add_hwgenerator_randomness(const void *buffer, size_t count, - size_t entropy); #if IS_ENABLED(CONFIG_VMGENID) extern void add_vmfork_randomness(const void *unique_vm_id, size_t size); extern int register_random_vmfork_notifier(struct notifier_block *nb); @@ -41,7 +40,7 @@ static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { extern void get_random_bytes(void *buf, size_t nbytes); extern int wait_for_random_bytes(void); -extern int __init rand_initialize(void); +extern int __init random_init(const char *command_line); extern bool rng_is_initialized(void); extern int register_random_ready_notifier(struct notifier_block *nb); extern int unregister_random_ready_notifier(struct notifier_block *nb); diff --git a/init/main.c b/init/main.c index 92783732a36f..f057c49f1d9d 100644 --- a/init/main.c +++ b/init/main.c @@ -1040,15 +1040,11 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void) /* * For best initial stack canary entropy, prepare it after: * - setup_arch() for any UEFI RNG entropy and boot cmdline access - * - timekeeping_init() for ktime entropy used in rand_initialize() + * - timekeeping_init() for ktime entropy used in random_init() * - time_init() for making random_get_entropy() work on some platforms - * - rand_initialize() to get any arch-specific entropy like RDRAND - * - add_latent_entropy() to get any latent entropy - * - adding command line entropy + * - random_init() to initialize the RNG from from early entropy sources */ - rand_initialize(); - add_latent_entropy(); - add_device_randomness(command_line, strlen(command_line)); + random_init(command_line); boot_init_stack_canary(); perf_event_init(); -- cgit v1.2.3 From 7782cfeca7d420e8bb707613d4cfb0f7ff29bb3a Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Fri, 13 May 2022 12:29:38 +0200 Subject: random: remove extern from functions in header Accoriding to the kernel style guide, having `extern` on functions in headers is old school and deprecated, and doesn't add anything. So remove them from random.h, and tidy up the file a little bit too. Signed-off-by: Jason A. Donenfeld --- include/linux/random.h | 77 ++++++++++++++++++++------------------------------ 1 file changed, 31 insertions(+), 46 deletions(-) (limited to 'include/linux') diff --git a/include/linux/random.h b/include/linux/random.h index b52963955a99..97f879ea78a5 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -12,13 +12,12 @@ struct notifier_block; -extern void add_device_randomness(const void *, size_t); -extern void add_bootloader_randomness(const void *, size_t); -extern void add_input_randomness(unsigned int type, unsigned int code, - unsigned int value) __latent_entropy; -extern void add_interrupt_randomness(int irq) __latent_entropy; -extern void add_hwgenerator_randomness(const void *buffer, size_t count, - size_t entropy); +void add_device_randomness(const void *, size_t); +void add_bootloader_randomness(const void *, size_t); +void add_input_randomness(unsigned int type, unsigned int code, + unsigned int value) __latent_entropy; +void add_interrupt_randomness(int irq) __latent_entropy; +void add_hwgenerator_randomness(const void *buffer, size_t count, size_t entropy); #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) static inline void add_latent_entropy(void) @@ -26,30 +25,20 @@ static inline void add_latent_entropy(void) add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); } #else -static inline void add_latent_entropy(void) {} +static inline void add_latent_entropy(void) { } #endif #if IS_ENABLED(CONFIG_VMGENID) -extern void add_vmfork_randomness(const void *unique_vm_id, size_t size); -extern int register_random_vmfork_notifier(struct notifier_block *nb); -extern int unregister_random_vmfork_notifier(struct notifier_block *nb); +void add_vmfork_randomness(const void *unique_vm_id, size_t size); +int register_random_vmfork_notifier(struct notifier_block *nb); +int unregister_random_vmfork_notifier(struct notifier_block *nb); #else static inline int register_random_vmfork_notifier(struct notifier_block *nb) { return 0; } static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { return 0; } #endif -extern void get_random_bytes(void *buf, size_t nbytes); -extern int wait_for_random_bytes(void); -extern int __init random_init(const char *command_line); -extern bool rng_is_initialized(void); -extern int register_random_ready_notifier(struct notifier_block *nb); -extern int unregister_random_ready_notifier(struct notifier_block *nb); -extern size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes); - -#ifndef MODULE -extern const struct file_operations random_fops, urandom_fops; -#endif - +void get_random_bytes(void *buf, size_t nbytes); +size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes); u32 get_random_u32(void); u64 get_random_u64(void); static inline unsigned int get_random_int(void) @@ -81,11 +70,17 @@ static inline unsigned long get_random_long(void) static inline unsigned long get_random_canary(void) { - unsigned long val = get_random_long(); - - return val & CANARY_MASK; + return get_random_long() & CANARY_MASK; } +unsigned long randomize_page(unsigned long start, unsigned long range); + +int __init random_init(const char *command_line); +bool rng_is_initialized(void); +int wait_for_random_bytes(void); +int register_random_ready_notifier(struct notifier_block *nb); +int unregister_random_ready_notifier(struct notifier_block *nb); + /* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes). * Returns the result of the call to wait_for_random_bytes. */ static inline int get_random_bytes_wait(void *buf, size_t nbytes) @@ -109,8 +104,6 @@ declare_get_random_var_wait(int) declare_get_random_var_wait(long) #undef declare_get_random_var -unsigned long randomize_page(unsigned long start, unsigned long range); - /* * This is designed to be standalone for just prandom * users, but for now we include it from @@ -121,22 +114,10 @@ unsigned long randomize_page(unsigned long start, unsigned long range); #ifdef CONFIG_ARCH_RANDOM # include #else -static inline bool __must_check arch_get_random_long(unsigned long *v) -{ - return false; -} -static inline bool __must_check arch_get_random_int(unsigned int *v) -{ - return false; -} -static inline bool __must_check arch_get_random_seed_long(unsigned long *v) -{ - return false; -} -static inline bool __must_check arch_get_random_seed_int(unsigned int *v) -{ - return false; -} +static inline bool __must_check arch_get_random_long(unsigned long *v) { return false; } +static inline bool __must_check arch_get_random_int(unsigned int *v) { return false; } +static inline bool __must_check arch_get_random_seed_long(unsigned long *v) { return false; } +static inline bool __must_check arch_get_random_seed_int(unsigned int *v) { return false; } #endif /* @@ -160,8 +141,12 @@ static inline bool __init arch_get_random_long_early(unsigned long *v) #endif #ifdef CONFIG_SMP -extern int random_prepare_cpu(unsigned int cpu); -extern int random_online_cpu(unsigned int cpu); +int random_prepare_cpu(unsigned int cpu); +int random_online_cpu(unsigned int cpu); +#endif + +#ifndef MODULE +extern const struct file_operations random_fops, urandom_fops; #endif #endif /* _LINUX_RANDOM_H */ -- cgit v1.2.3 From 7c3a8a1db5e03d02cc0abb3357a84b8b326dfac3 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Fri, 13 May 2022 12:32:23 +0200 Subject: random: use proper return types on get_random_{int,long}_wait() Before these were returning signed values, but the API is intended to be used with unsigned values. Signed-off-by: Jason A. Donenfeld --- include/linux/random.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'include/linux') diff --git a/include/linux/random.h b/include/linux/random.h index 97f879ea78a5..883bf9a23d84 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -90,18 +90,18 @@ static inline int get_random_bytes_wait(void *buf, size_t nbytes) return ret; } -#define declare_get_random_var_wait(var) \ - static inline int get_random_ ## var ## _wait(var *out) { \ +#define declare_get_random_var_wait(name, ret_type) \ + static inline int get_random_ ## name ## _wait(ret_type *out) { \ int ret = wait_for_random_bytes(); \ if (unlikely(ret)) \ return ret; \ - *out = get_random_ ## var(); \ + *out = get_random_ ## name(); \ return 0; \ } -declare_get_random_var_wait(u32) -declare_get_random_var_wait(u64) -declare_get_random_var_wait(int) -declare_get_random_var_wait(long) +declare_get_random_var_wait(u32, u32) +declare_get_random_var_wait(u64, u32) +declare_get_random_var_wait(int, unsigned int) +declare_get_random_var_wait(long, unsigned long) #undef declare_get_random_var /* -- cgit v1.2.3 From a19402634c435a4eae226df53c141cdbb9922e7b Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Fri, 13 May 2022 13:18:46 +0200 Subject: random: make consistent use of buf and len The current code was a mix of "nbytes", "count", "size", "buffer", "in", and so forth. Instead, let's clean this up by naming input parameters "buf" (or "ubuf") and "len", so that you always understand that you're reading this variety of function argument. Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 199 ++++++++++++++++++++++++------------------------- include/linux/random.h | 12 +-- 2 files changed, 103 insertions(+), 108 deletions(-) (limited to 'include/linux') diff --git a/drivers/char/random.c b/drivers/char/random.c index b2cfd659bae5..0475ed69aa34 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -209,7 +209,7 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller) * * There are a few exported interfaces for use by other drivers: * - * void get_random_bytes(void *buf, size_t nbytes) + * void get_random_bytes(void *buf, size_t len) * u32 get_random_u32() * u64 get_random_u64() * unsigned int get_random_int() @@ -250,7 +250,7 @@ static DEFINE_PER_CPU(struct crng, crngs) = { }; /* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */ -static void extract_entropy(void *buf, size_t nbytes); +static void extract_entropy(void *buf, size_t len); /* This extracts a new crng key from the input pool. */ static void crng_reseed(void) @@ -404,24 +404,24 @@ static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS], local_unlock_irqrestore(&crngs.lock, flags); } -static void _get_random_bytes(void *buf, size_t nbytes) +static void _get_random_bytes(void *buf, size_t len) { u32 chacha_state[CHACHA_STATE_WORDS]; u8 tmp[CHACHA_BLOCK_SIZE]; - size_t len; + size_t first_block_len; - if (!nbytes) + if (!len) return; - len = min_t(size_t, 32, nbytes); - crng_make_state(chacha_state, buf, len); - nbytes -= len; - buf += len; + first_block_len = min_t(size_t, 32, len); + crng_make_state(chacha_state, buf, first_block_len); + len -= first_block_len; + buf += first_block_len; - while (nbytes) { - if (nbytes < CHACHA_BLOCK_SIZE) { + while (len) { + if (len < CHACHA_BLOCK_SIZE) { chacha20_block(chacha_state, tmp); - memcpy(buf, tmp, nbytes); + memcpy(buf, tmp, len); memzero_explicit(tmp, sizeof(tmp)); break; } @@ -429,7 +429,7 @@ static void _get_random_bytes(void *buf, size_t nbytes) chacha20_block(chacha_state, buf); if (unlikely(chacha_state[12] == 0)) ++chacha_state[13]; - nbytes -= CHACHA_BLOCK_SIZE; + len -= CHACHA_BLOCK_SIZE; buf += CHACHA_BLOCK_SIZE; } @@ -446,20 +446,20 @@ static void _get_random_bytes(void *buf, size_t nbytes) * wait_for_random_bytes() should be called and return 0 at least once * at any point prior. */ -void get_random_bytes(void *buf, size_t nbytes) +void get_random_bytes(void *buf, size_t len) { warn_unseeded_randomness(); - _get_random_bytes(buf, nbytes); + _get_random_bytes(buf, len); } EXPORT_SYMBOL(get_random_bytes); -static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) +static ssize_t get_random_bytes_user(void __user *ubuf, size_t len) { - size_t len, left, ret = 0; + size_t block_len, left, ret = 0; u32 chacha_state[CHACHA_STATE_WORDS]; u8 output[CHACHA_BLOCK_SIZE]; - if (!nbytes) + if (!len) return 0; /* @@ -473,8 +473,8 @@ static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) * use chacha_state after, so we can simply return those bytes to * the user directly. */ - if (nbytes <= CHACHA_KEY_SIZE) { - ret = nbytes - copy_to_user(buf, &chacha_state[4], nbytes); + if (len <= CHACHA_KEY_SIZE) { + ret = len - copy_to_user(ubuf, &chacha_state[4], len); goto out_zero_chacha; } @@ -483,17 +483,17 @@ static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) if (unlikely(chacha_state[12] == 0)) ++chacha_state[13]; - len = min_t(size_t, nbytes, CHACHA_BLOCK_SIZE); - left = copy_to_user(buf, output, len); + block_len = min_t(size_t, len, CHACHA_BLOCK_SIZE); + left = copy_to_user(ubuf, output, block_len); if (left) { - ret += len - left; + ret += block_len - left; break; } - buf += len; - ret += len; - nbytes -= len; - if (!nbytes) + ubuf += block_len; + ret += block_len; + len -= block_len; + if (!len) break; BUILD_BUG_ON(PAGE_SIZE % CHACHA_BLOCK_SIZE != 0); @@ -667,24 +667,24 @@ unsigned long randomize_page(unsigned long start, unsigned long range) * use. Use get_random_bytes() instead. It returns the number of * bytes filled in. */ -size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes) +size_t __must_check get_random_bytes_arch(void *buf, size_t len) { - size_t left = nbytes; + size_t left = len; u8 *p = buf; while (left) { unsigned long v; - size_t chunk = min_t(size_t, left, sizeof(unsigned long)); + size_t block_len = min_t(size_t, left, sizeof(unsigned long)); if (!arch_get_random_long(&v)) break; - memcpy(p, &v, chunk); - p += chunk; - left -= chunk; + memcpy(p, &v, block_len); + p += block_len; + left -= block_len; } - return nbytes - left; + return len - left; } EXPORT_SYMBOL(get_random_bytes_arch); @@ -695,15 +695,15 @@ EXPORT_SYMBOL(get_random_bytes_arch); * * Callers may add entropy via: * - * static void mix_pool_bytes(const void *in, size_t nbytes) + * static void mix_pool_bytes(const void *buf, size_t len) * * After which, if added entropy should be credited: * - * static void credit_init_bits(size_t nbits) + * static void credit_init_bits(size_t bits) * * Finally, extract entropy via: * - * static void extract_entropy(void *buf, size_t nbytes) + * static void extract_entropy(void *buf, size_t len) * **********************************************************************/ @@ -725,9 +725,9 @@ static struct { .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), }; -static void _mix_pool_bytes(const void *in, size_t nbytes) +static void _mix_pool_bytes(const void *buf, size_t len) { - blake2s_update(&input_pool.hash, in, nbytes); + blake2s_update(&input_pool.hash, buf, len); } /* @@ -735,12 +735,12 @@ static void _mix_pool_bytes(const void *in, size_t nbytes) * update the initialization bit counter; the caller should call * credit_init_bits if this is appropriate. */ -static void mix_pool_bytes(const void *in, size_t nbytes) +static void mix_pool_bytes(const void *buf, size_t len) { unsigned long flags; spin_lock_irqsave(&input_pool.lock, flags); - _mix_pool_bytes(in, nbytes); + _mix_pool_bytes(buf, len); spin_unlock_irqrestore(&input_pool.lock, flags); } @@ -748,7 +748,7 @@ static void mix_pool_bytes(const void *in, size_t nbytes) * This is an HKDF-like construction for using the hashed collected entropy * as a PRF key, that's then expanded block-by-block. */ -static void extract_entropy(void *buf, size_t nbytes) +static void extract_entropy(void *buf, size_t len) { unsigned long flags; u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; @@ -777,12 +777,12 @@ static void extract_entropy(void *buf, size_t nbytes) spin_unlock_irqrestore(&input_pool.lock, flags); memzero_explicit(next_key, sizeof(next_key)); - while (nbytes) { - i = min_t(size_t, nbytes, BLAKE2S_HASH_SIZE); + while (len) { + i = min_t(size_t, len, BLAKE2S_HASH_SIZE); /* output = HASHPRF(seed, RDSEED || ++counter) */ ++block.counter; blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed)); - nbytes -= i; + len -= i; buf += i; } @@ -790,16 +790,16 @@ static void extract_entropy(void *buf, size_t nbytes) memzero_explicit(&block, sizeof(block)); } -static void credit_init_bits(size_t nbits) +static void credit_init_bits(size_t bits) { static struct execute_work set_ready; unsigned int new, orig, add; unsigned long flags; - if (crng_ready() || !nbits) + if (crng_ready() || !bits) return; - add = min_t(size_t, nbits, POOL_BITS); + add = min_t(size_t, bits, POOL_BITS); do { orig = READ_ONCE(input_pool.init_bits); @@ -835,14 +835,12 @@ static void credit_init_bits(size_t nbits) * The following exported functions are used for pushing entropy into * the above entropy accumulation routines: * - * void add_device_randomness(const void *buf, size_t size); - * void add_hwgenerator_randomness(const void *buffer, size_t count, - * size_t entropy); - * void add_bootloader_randomness(const void *buf, size_t size); - * void add_vmfork_randomness(const void *unique_vm_id, size_t size); + * void add_device_randomness(const void *buf, size_t len); + * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy); + * void add_bootloader_randomness(const void *buf, size_t len); + * void add_vmfork_randomness(const void *unique_vm_id, size_t len); * void add_interrupt_randomness(int irq); - * void add_input_randomness(unsigned int type, unsigned int code, - * unsigned int value); + * void add_input_randomness(unsigned int type, unsigned int code, unsigned int value); * void add_disk_randomness(struct gendisk *disk); * * add_device_randomness() adds data to the input pool that @@ -937,7 +935,7 @@ int __init random_init(const char *command_line) { ktime_t now = ktime_get_real(); unsigned int i, arch_bytes; - unsigned long rv; + unsigned long entropy; #if defined(LATENT_ENTROPY_PLUGIN) static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy; @@ -945,13 +943,13 @@ int __init random_init(const char *command_line) #endif for (i = 0, arch_bytes = BLAKE2S_BLOCK_SIZE; - i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) { - if (!arch_get_random_seed_long_early(&rv) && - !arch_get_random_long_early(&rv)) { - rv = random_get_entropy(); - arch_bytes -= sizeof(rv); + i < BLAKE2S_BLOCK_SIZE; i += sizeof(entropy)) { + if (!arch_get_random_seed_long_early(&entropy) && + !arch_get_random_long_early(&entropy)) { + entropy = random_get_entropy(); + arch_bytes -= sizeof(entropy); } - _mix_pool_bytes(&rv, sizeof(rv)); + _mix_pool_bytes(&entropy, sizeof(entropy)); } _mix_pool_bytes(&now, sizeof(now)); _mix_pool_bytes(utsname(), sizeof(*(utsname()))); @@ -978,14 +976,14 @@ int __init random_init(const char *command_line) * the entropy pool having similar initial state across largely * identical devices. */ -void add_device_randomness(const void *buf, size_t size) +void add_device_randomness(const void *buf, size_t len) { unsigned long entropy = random_get_entropy(); unsigned long flags; spin_lock_irqsave(&input_pool.lock, flags); _mix_pool_bytes(&entropy, sizeof(entropy)); - _mix_pool_bytes(buf, size); + _mix_pool_bytes(buf, len); spin_unlock_irqrestore(&input_pool.lock, flags); } EXPORT_SYMBOL(add_device_randomness); @@ -995,10 +993,9 @@ EXPORT_SYMBOL(add_device_randomness); * Those devices may produce endless random bits and will be throttled * when our pool is full. */ -void add_hwgenerator_randomness(const void *buffer, size_t count, - size_t entropy) +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy) { - mix_pool_bytes(buffer, count); + mix_pool_bytes(buf, len); credit_init_bits(entropy); /* @@ -1014,11 +1011,11 @@ EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); * Handle random seed passed by bootloader, and credit it if * CONFIG_RANDOM_TRUST_BOOTLOADER is set. */ -void add_bootloader_randomness(const void *buf, size_t size) +void add_bootloader_randomness(const void *buf, size_t len) { - mix_pool_bytes(buf, size); + mix_pool_bytes(buf, len); if (trust_bootloader) - credit_init_bits(size * 8); + credit_init_bits(len * 8); } EXPORT_SYMBOL_GPL(add_bootloader_randomness); @@ -1030,9 +1027,9 @@ static BLOCKING_NOTIFIER_HEAD(vmfork_chain); * don't credit it, but we do immediately force a reseed after so * that it's used by the crng posthaste. */ -void add_vmfork_randomness(const void *unique_vm_id, size_t size) +void add_vmfork_randomness(const void *unique_vm_id, size_t len) { - add_device_randomness(unique_vm_id, size); + add_device_randomness(unique_vm_id, len); if (crng_ready()) { crng_reseed(); pr_notice("crng reseeded due to virtual machine fork\n"); @@ -1252,8 +1249,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned int nu credit_init_bits(bits); } -void add_input_randomness(unsigned int type, unsigned int code, - unsigned int value) +void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) { static unsigned char last_value; static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES }; @@ -1388,8 +1384,7 @@ static void try_to_generate_entropy(void) * **********************************************************************/ -SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, - flags) +SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags) { if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) return -EINVAL; @@ -1401,8 +1396,8 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) return -EINVAL; - if (count > INT_MAX) - count = INT_MAX; + if (len > INT_MAX) + len = INT_MAX; if (!crng_ready() && !(flags & GRND_INSECURE)) { int ret; @@ -1413,7 +1408,7 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, if (unlikely(ret)) return ret; } - return get_random_bytes_user(buf, count); + return get_random_bytes_user(ubuf, len); } static __poll_t random_poll(struct file *file, poll_table *wait) @@ -1422,21 +1417,21 @@ static __poll_t random_poll(struct file *file, poll_table *wait) return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM; } -static int write_pool(const char __user *ubuf, size_t count) +static int write_pool(const char __user *ubuf, size_t len) { - size_t len; + size_t block_len; int ret = 0; u8 block[BLAKE2S_BLOCK_SIZE]; - while (count) { - len = min(count, sizeof(block)); - if (copy_from_user(block, ubuf, len)) { + while (len) { + block_len = min(len, sizeof(block)); + if (copy_from_user(block, ubuf, block_len)) { ret = -EFAULT; goto out; } - count -= len; - ubuf += len; - mix_pool_bytes(block, len); + len -= block_len; + ubuf += block_len; + mix_pool_bytes(block, block_len); cond_resched(); } @@ -1445,20 +1440,20 @@ out: return ret; } -static ssize_t random_write(struct file *file, const char __user *buffer, - size_t count, loff_t *ppos) +static ssize_t random_write(struct file *file, const char __user *ubuf, + size_t len, loff_t *ppos) { int ret; - ret = write_pool(buffer, count); + ret = write_pool(ubuf, len); if (ret) return ret; - return (ssize_t)count; + return (ssize_t)len; } -static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, - loff_t *ppos) +static ssize_t urandom_read(struct file *file, char __user *ubuf, + size_t len, loff_t *ppos) { static int maxwarn = 10; @@ -1475,22 +1470,22 @@ static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, else if (ratelimit_disable || __ratelimit(&urandom_warning)) { --maxwarn; pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", - current->comm, nbytes); + current->comm, len); } } - return get_random_bytes_user(buf, nbytes); + return get_random_bytes_user(ubuf, len); } -static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, - loff_t *ppos) +static ssize_t random_read(struct file *file, char __user *ubuf, + size_t len, loff_t *ppos) { int ret; ret = wait_for_random_bytes(); if (ret != 0) return ret; - return get_random_bytes_user(buf, nbytes); + return get_random_bytes_user(ubuf, len); } static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) @@ -1615,7 +1610,7 @@ static u8 sysctl_bootid[UUID_SIZE]; * UUID. The difference is in whether table->data is NULL; if it is, * then a new UUID is generated and returned to the user. */ -static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, +static int proc_do_uuid(struct ctl_table *table, int write, void *buf, size_t *lenp, loff_t *ppos) { u8 tmp_uuid[UUID_SIZE], *uuid; @@ -1642,14 +1637,14 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, } snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid); - return proc_dostring(&fake_table, 0, buffer, lenp, ppos); + return proc_dostring(&fake_table, 0, buf, lenp, ppos); } /* The same as proc_dointvec, but writes don't change anything. */ -static int proc_do_rointvec(struct ctl_table *table, int write, void *buffer, +static int proc_do_rointvec(struct ctl_table *table, int write, void *buf, size_t *lenp, loff_t *ppos) { - return write ? 0 : proc_dointvec(table, 0, buffer, lenp, ppos); + return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos); } static struct ctl_table random_table[] = { diff --git a/include/linux/random.h b/include/linux/random.h index 883bf9a23d84..fc82f1dc36f1 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -12,12 +12,12 @@ struct notifier_block; -void add_device_randomness(const void *, size_t); -void add_bootloader_randomness(const void *, size_t); +void add_device_randomness(const void *buf, size_t len); +void add_bootloader_randomness(const void *buf, size_t len); void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) __latent_entropy; void add_interrupt_randomness(int irq) __latent_entropy; -void add_hwgenerator_randomness(const void *buffer, size_t count, size_t entropy); +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy); #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) static inline void add_latent_entropy(void) @@ -29,7 +29,7 @@ static inline void add_latent_entropy(void) { } #endif #if IS_ENABLED(CONFIG_VMGENID) -void add_vmfork_randomness(const void *unique_vm_id, size_t size); +void add_vmfork_randomness(const void *unique_vm_id, size_t len); int register_random_vmfork_notifier(struct notifier_block *nb); int unregister_random_vmfork_notifier(struct notifier_block *nb); #else @@ -37,8 +37,8 @@ static inline int register_random_vmfork_notifier(struct notifier_block *nb) { r static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { return 0; } #endif -void get_random_bytes(void *buf, size_t nbytes); -size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes); +void get_random_bytes(void *buf, size_t len); +size_t __must_check get_random_bytes_arch(void *buf, size_t len); u32 get_random_u32(void); u64 get_random_u64(void); static inline unsigned int get_random_int(void) -- cgit v1.2.3 From 248561ad25a8ba4ecbc7df42f9a5a82fd5fbb4f6 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sat, 14 May 2022 13:09:17 +0200 Subject: random: remove get_random_bytes_arch() and add rng_has_arch_random() The RNG incorporates RDRAND into its state at boot and every time it reseeds, so there's no reason for callers to use it directly. The hashing that the RNG does on it is preferable to using the bytes raw. The only current use case of get_random_bytes_arch() is vsprintf's siphash key for pointer hashing, which uses it to initialize the pointer secret earlier than usual if RDRAND is available. In order to replace this narrow use case, just expose whether RDRAND is mixed into the RNG, with a new function called rng_has_arch_random(). With that taken care of, there are no users of get_random_bytes_arch() left, so it can be removed. Later, if trust_cpu gets turned on by default (as most distros are doing), this one use of rng_has_arch_random() can probably go away as well. Cc: Steven Rostedt Cc: Sergey Senozhatsky Acked-by: Petr Mladek # for vsprintf.c Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 49 ++++++++++++++++--------------------------------- include/linux/random.h | 2 +- lib/vsprintf.c | 7 +++---- 3 files changed, 20 insertions(+), 38 deletions(-) (limited to 'include/linux') diff --git a/drivers/char/random.c b/drivers/char/random.c index 7ec700683e42..6b8c89378954 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -433,12 +433,9 @@ static void _get_random_bytes(void *buf, size_t len) /* * This function is the exported kernel interface. It returns some * number of good random numbers, suitable for key generation, seeding - * TCP sequence numbers, etc. It does not rely on the hardware random - * number generator. For random bytes direct from the hardware RNG - * (when available), use get_random_bytes_arch(). In order to ensure - * that the randomness provided by this function is okay, the function - * wait_for_random_bytes() should be called and return 0 at least once - * at any point prior. + * TCP sequence numbers, etc. In order to ensure that the randomness + * by this function is okay, the function wait_for_random_bytes() + * should be called and return 0 at least once at any point prior. */ void get_random_bytes(void *buf, size_t len) { @@ -655,33 +652,6 @@ unsigned long randomize_page(unsigned long start, unsigned long range) return start + (get_random_long() % range << PAGE_SHIFT); } -/* - * This function will use the architecture-specific hardware random - * number generator if it is available. It is not recommended for - * use. Use get_random_bytes() instead. It returns the number of - * bytes filled in. - */ -size_t __must_check get_random_bytes_arch(void *buf, size_t len) -{ - size_t left = len; - u8 *p = buf; - - while (left) { - unsigned long v; - size_t block_len = min_t(size_t, left, sizeof(unsigned long)); - - if (!arch_get_random_long(&v)) - break; - - memcpy(p, &v, block_len); - p += block_len; - left -= block_len; - } - - return len - left; -} -EXPORT_SYMBOL(get_random_bytes_arch); - /********************************************************************** * @@ -879,6 +849,7 @@ static void __cold _credit_init_bits(size_t bits) * **********************************************************************/ +static bool used_arch_random; static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); static bool trust_bootloader __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER); static int __init parse_trust_cpu(char *arg) @@ -956,6 +927,7 @@ int __init random_init(const char *command_line) crng_reseed(); else if (trust_cpu) credit_init_bits(arch_bytes * 8); + used_arch_random = arch_bytes * 8 >= POOL_READY_BITS; WARN_ON(register_pm_notifier(&pm_notifier)); @@ -964,6 +936,17 @@ int __init random_init(const char *command_line) return 0; } +/* + * Returns whether arch randomness has been mixed into the initial + * state of the RNG, regardless of whether or not that randomness + * was credited. Knowing this is only good for a very limited set + * of uses, such as early init printk pointer obfuscation. + */ +bool rng_has_arch_random(void) +{ + return used_arch_random; +} + /* * Add device- or boot-specific data to the input pool to help * initialize it. diff --git a/include/linux/random.h b/include/linux/random.h index fc82f1dc36f1..6af130c6edb9 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -38,7 +38,6 @@ static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { #endif void get_random_bytes(void *buf, size_t len); -size_t __must_check get_random_bytes_arch(void *buf, size_t len); u32 get_random_u32(void); u64 get_random_u64(void); static inline unsigned int get_random_int(void) @@ -77,6 +76,7 @@ unsigned long randomize_page(unsigned long start, unsigned long range); int __init random_init(const char *command_line); bool rng_is_initialized(void); +bool rng_has_arch_random(void); int wait_for_random_bytes(void); int register_random_ready_notifier(struct notifier_block *nb); int unregister_random_ready_notifier(struct notifier_block *nb); diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 40d26a07a133..20e9887faaaa 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -776,12 +776,11 @@ static struct notifier_block random_ready = { static int __init initialize_ptr_random(void) { - int key_size = sizeof(ptr_key); int ret; - /* Use hw RNG if available. */ - if (get_random_bytes_arch(&ptr_key, key_size) == key_size) { - static_branch_disable(¬_filled_random_ptr_key); + /* Don't bother waiting for RNG to be ready if RDRAND is mixed in already. */ + if (rng_has_arch_random()) { + enable_ptr_key_workfn(&enable_ptr_key_work); return 0; } -- cgit v1.2.3 From 6701de6c51c172b5de5633374479503c81fefc0b Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sun, 15 May 2022 15:06:18 +0200 Subject: random: remove mostly unused async readiness notifier The register_random_ready_notifier() notifier is somewhat complicated, and was already recently rewritten to use notifier blocks. It is only used now by one consumer in the kernel, vsprintf.c, for which the async mechanism is really overly complex for what it actually needs. This commit removes register_random_ready_notifier() and unregister_random_ ready_notifier(), because it just adds complication with little utility, and changes vsprintf.c to just check on `!rng_is_initialized() && !rng_has_arch_random()`, which will eventually be true. Performance- wise, that code was already using a static branch, so there's basically no overhead at all to this change. Cc: Steven Rostedt Cc: Sergey Senozhatsky Acked-by: Petr Mladek # for vsprintf.c Reviewed-by: Petr Mladek Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 48 ------------------------------------ include/linux/random.h | 2 -- lib/vsprintf.c | 66 +++++++++++++++++--------------------------------- 3 files changed, 22 insertions(+), 94 deletions(-) (limited to 'include/linux') diff --git a/drivers/char/random.c b/drivers/char/random.c index 6b8c89378954..16b39d2dead7 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -84,8 +84,6 @@ static DEFINE_STATIC_KEY_FALSE(crng_is_ready); /* Various types of waiters for crng_init->CRNG_READY transition. */ static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); static struct fasync_struct *fasync; -static DEFINE_SPINLOCK(random_ready_chain_lock); -static RAW_NOTIFIER_HEAD(random_ready_chain); /* Control how we warn userspace. */ static struct ratelimit_state urandom_warning = @@ -142,51 +140,6 @@ int wait_for_random_bytes(void) } EXPORT_SYMBOL(wait_for_random_bytes); -/* - * Add a callback function that will be invoked when the input - * pool is initialised. - * - * returns: 0 if callback is successfully added - * -EALREADY if pool is already initialised (callback not called) - */ -int __cold register_random_ready_notifier(struct notifier_block *nb) -{ - unsigned long flags; - int ret = -EALREADY; - - if (crng_ready()) - return ret; - - spin_lock_irqsave(&random_ready_chain_lock, flags); - if (!crng_ready()) - ret = raw_notifier_chain_register(&random_ready_chain, nb); - spin_unlock_irqrestore(&random_ready_chain_lock, flags); - return ret; -} - -/* - * Delete a previously registered readiness callback function. - */ -int __cold unregister_random_ready_notifier(struct notifier_block *nb) -{ - unsigned long flags; - int ret; - - spin_lock_irqsave(&random_ready_chain_lock, flags); - ret = raw_notifier_chain_unregister(&random_ready_chain, nb); - spin_unlock_irqrestore(&random_ready_chain_lock, flags); - return ret; -} - -static void __cold process_random_ready_list(void) -{ - unsigned long flags; - - spin_lock_irqsave(&random_ready_chain_lock, flags); - raw_notifier_call_chain(&random_ready_chain, 0, NULL); - spin_unlock_irqrestore(&random_ready_chain_lock, flags); -} - #define warn_unseeded_randomness() \ if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \ printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \ @@ -775,7 +728,6 @@ static void __cold _credit_init_bits(size_t bits) if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) { crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */ execute_in_process_context(crng_set_ready, &set_ready); - process_random_ready_list(); wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN); pr_notice("crng init done\n"); diff --git a/include/linux/random.h b/include/linux/random.h index 6af130c6edb9..d2360b2825b6 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -78,8 +78,6 @@ int __init random_init(const char *command_line); bool rng_is_initialized(void); bool rng_has_arch_random(void); int wait_for_random_bytes(void); -int register_random_ready_notifier(struct notifier_block *nb); -int unregister_random_ready_notifier(struct notifier_block *nb); /* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes). * Returns the result of the call to wait_for_random_bytes. */ diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 20e9887faaaa..fb77f7bfd126 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -750,60 +750,38 @@ static int __init debug_boot_weak_hash_enable(char *str) } early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable); -static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key); -static siphash_key_t ptr_key __read_mostly; +static DEFINE_STATIC_KEY_FALSE(filled_random_ptr_key); static void enable_ptr_key_workfn(struct work_struct *work) { - get_random_bytes(&ptr_key, sizeof(ptr_key)); - /* Needs to run from preemptible context */ - static_branch_disable(¬_filled_random_ptr_key); + static_branch_enable(&filled_random_ptr_key); } -static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn); - -static int fill_random_ptr_key(struct notifier_block *nb, - unsigned long action, void *data) -{ - /* This may be in an interrupt handler. */ - queue_work(system_unbound_wq, &enable_ptr_key_work); - return 0; -} - -static struct notifier_block random_ready = { - .notifier_call = fill_random_ptr_key -}; - -static int __init initialize_ptr_random(void) -{ - int ret; - - /* Don't bother waiting for RNG to be ready if RDRAND is mixed in already. */ - if (rng_has_arch_random()) { - enable_ptr_key_workfn(&enable_ptr_key_work); - return 0; - } - - ret = register_random_ready_notifier(&random_ready); - if (!ret) { - return 0; - } else if (ret == -EALREADY) { - /* This is in preemptible context */ - enable_ptr_key_workfn(&enable_ptr_key_work); - return 0; - } - - return ret; -} -early_initcall(initialize_ptr_random); - /* Maps a pointer to a 32 bit unique identifier. */ static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out) { + static siphash_key_t ptr_key __read_mostly; unsigned long hashval; - if (static_branch_unlikely(¬_filled_random_ptr_key)) - return -EAGAIN; + if (!static_branch_likely(&filled_random_ptr_key)) { + static bool filled = false; + static DEFINE_SPINLOCK(filling); + static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn); + unsigned long flags; + + if (!system_unbound_wq || + (!rng_is_initialized() && !rng_has_arch_random()) || + !spin_trylock_irqsave(&filling, flags)) + return -EAGAIN; + + if (!filled) { + get_random_bytes(&ptr_key, sizeof(ptr_key)); + queue_work(system_unbound_wq, &enable_ptr_key_work); + filled = true; + } + spin_unlock_irqrestore(&filling, flags); + } + #ifdef CONFIG_64BIT hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key); -- cgit v1.2.3 From 5ad7dd882e45d7fe432c32e896e2aaa0b21746ea Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sat, 14 May 2022 13:59:30 +0200 Subject: random: move randomize_page() into mm where it belongs randomize_page is an mm function. It is documented like one. It contains the history of one. It has the naming convention of one. It looks just like another very similar function in mm, randomize_stack_top(). And it has always been maintained and updated by mm people. There is no need for it to be in random.c. In the "which shape does not look like the other ones" test, pointing to randomize_page() is correct. So move randomize_page() into mm/util.c, right next to the similar randomize_stack_top() function. This commit contains no actual code changes. Cc: Andrew Morton Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 32 -------------------------------- include/linux/mm.h | 1 + include/linux/random.h | 2 -- mm/util.c | 32 ++++++++++++++++++++++++++++++++ 4 files changed, 33 insertions(+), 34 deletions(-) (limited to 'include/linux') diff --git a/drivers/char/random.c b/drivers/char/random.c index 16b39d2dead7..36183b0cf923 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -573,38 +573,6 @@ int __cold random_prepare_cpu(unsigned int cpu) } #endif -/** - * randomize_page - Generate a random, page aligned address - * @start: The smallest acceptable address the caller will take. - * @range: The size of the area, starting at @start, within which the - * random address must fall. - * - * If @start + @range would overflow, @range is capped. - * - * NOTE: Historical use of randomize_range, which this replaces, presumed that - * @start was already page aligned. We now align it regardless. - * - * Return: A page aligned address within [start, start + range). On error, - * @start is returned. - */ -unsigned long randomize_page(unsigned long start, unsigned long range) -{ - if (!PAGE_ALIGNED(start)) { - range -= PAGE_ALIGN(start) - start; - start = PAGE_ALIGN(start); - } - - if (start > ULONG_MAX - range) - range = ULONG_MAX - start; - - range >>= PAGE_SHIFT; - - if (range == 0) - return start; - - return start + (get_random_long() % range << PAGE_SHIFT); -} - /********************************************************************** * diff --git a/include/linux/mm.h b/include/linux/mm.h index 9f44254af8ce..b0183450e484 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2677,6 +2677,7 @@ extern int install_special_mapping(struct mm_struct *mm, unsigned long flags, struct page **pages); unsigned long randomize_stack_top(unsigned long stack_top); +unsigned long randomize_page(unsigned long start, unsigned long range); extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); diff --git a/include/linux/random.h b/include/linux/random.h index d2360b2825b6..fae0c84027fd 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -72,8 +72,6 @@ static inline unsigned long get_random_canary(void) return get_random_long() & CANARY_MASK; } -unsigned long randomize_page(unsigned long start, unsigned long range); - int __init random_init(const char *command_line); bool rng_is_initialized(void); bool rng_has_arch_random(void); diff --git a/mm/util.c b/mm/util.c index 3492a9e81aa3..ac63e5ca8b21 100644 --- a/mm/util.c +++ b/mm/util.c @@ -343,6 +343,38 @@ unsigned long randomize_stack_top(unsigned long stack_top) #endif } +/** + * randomize_page - Generate a random, page aligned address + * @start: The smallest acceptable address the caller will take. + * @range: The size of the area, starting at @start, within which the + * random address must fall. + * + * If @start + @range would overflow, @range is capped. + * + * NOTE: Historical use of randomize_range, which this replaces, presumed that + * @start was already page aligned. We now align it regardless. + * + * Return: A page aligned address within [start, start + range). On error, + * @start is returned. + */ +unsigned long randomize_page(unsigned long start, unsigned long range) +{ + if (!PAGE_ALIGNED(start)) { + range -= PAGE_ALIGN(start) - start; + start = PAGE_ALIGN(start); + } + + if (start > ULONG_MAX - range) + range = ULONG_MAX - start; + + range >>= PAGE_SHIFT; + + if (range == 0) + return start; + + return start + (get_random_long() % range << PAGE_SHIFT); +} + #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT unsigned long arch_randomize_brk(struct mm_struct *mm) { -- cgit v1.2.3