From 81895a65ec63ee1daec3255dc1a06675d2fbe915 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 5 Oct 2022 16:43:38 +0200 Subject: treewide: use prandom_u32_max() when possible, part 1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Rather than incurring a division or requesting too many random bytes for the given range, use the prandom_u32_max() function, which only takes the minimum required bytes from the RNG and avoids divisions. This was done mechanically with this coccinelle script: @basic@ expression E; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; typedef u64; @@ ( - ((T)get_random_u32() % (E)) + prandom_u32_max(E) | - ((T)get_random_u32() & ((E) - 1)) + prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2) | - ((u64)(E) * get_random_u32() >> 32) + prandom_u32_max(E) | - ((T)get_random_u32() & ~PAGE_MASK) + prandom_u32_max(PAGE_SIZE) ) @multi_line@ identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; identifier RAND; expression E; @@ - RAND = get_random_u32(); ... when != RAND - RAND %= (E); + RAND = prandom_u32_max(E); // Find a potential literal @literal_mask@ expression LITERAL; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; position p; @@ ((T)get_random_u32()@p & (LITERAL)) // Add one to the literal. @script:python add_one@ literal << literal_mask.LITERAL; RESULT; @@ value = None if literal.startswith('0x'): value = int(literal, 16) elif literal[0] in '123456789': value = int(literal, 10) if value is None: print("I don't know how to handle %s" % (literal)) cocci.include_match(False) elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1: print("Skipping 0x%x for cleanup elsewhere" % (value)) cocci.include_match(False) elif value & (value + 1) != 0: print("Skipping 0x%x because it's not a power of two minus one" % (value)) cocci.include_match(False) elif literal.startswith('0x'): coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1)) else: coccinelle.RESULT = cocci.make_expr("%d" % (value + 1)) // Replace the literal mask with the calculated result. @plus_one@ expression literal_mask.LITERAL; position literal_mask.p; expression add_one.RESULT; identifier FUNC; @@ - (FUNC()@p & (LITERAL)) + prandom_u32_max(RESULT) @collapse_ret@ type T; identifier VAR; expression E; @@ { - T VAR; - VAR = (E); - return VAR; + return E; } @drop_var@ type T; identifier VAR; @@ { - T VAR; ... when != VAR } Reviewed-by: Greg Kroah-Hartman Reviewed-by: Kees Cook Reviewed-by: Yury Norov Reviewed-by: KP Singh Reviewed-by: Jan Kara # for ext4 and sbitmap Reviewed-by: Christoph Böhmwalder # for drbd Acked-by: Jakub Kicinski Acked-by: Heiko Carstens # for s390 Acked-by: Ulf Hansson # for mmc Acked-by: Darrick J. Wong # for xfs Signed-off-by: Jason A. Donenfeld --- include/linux/nodemask.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h index 378956c93c94..efef68c9352a 100644 --- a/include/linux/nodemask.h +++ b/include/linux/nodemask.h @@ -516,7 +516,7 @@ static inline int node_random(const nodemask_t *maskp) bit = first_node(*maskp); break; default: - bit = find_nth_bit(maskp->bits, MAX_NUMNODES, get_random_int() % w); + bit = find_nth_bit(maskp->bits, MAX_NUMNODES, prandom_u32_max(w)); break; } return bit; -- cgit v1.2.3 From de492c83cae0af72de370b9404aacda93dafcad5 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 5 Oct 2022 17:50:20 +0200 Subject: prandom: remove unused functions With no callers left of prandom_u32() and prandom_bytes(), as well as get_random_int(), remove these deprecated wrappers, in favor of get_random_u32() and get_random_bytes(). Reviewed-by: Greg Kroah-Hartman Reviewed-by: Kees Cook Reviewed-by: Yury Norov Acked-by: Jakub Kicinski Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 11 +++++------ include/linux/prandom.h | 12 ------------ include/linux/random.h | 5 ----- 3 files changed, 5 insertions(+), 23 deletions(-) (limited to 'include/linux') diff --git a/drivers/char/random.c b/drivers/char/random.c index 01acf235f263..2fe28eeb2f38 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -97,7 +97,7 @@ MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression"); * Returns whether or not the input pool has been seeded and thus guaranteed * to supply cryptographically secure random numbers. This applies to: the * /dev/urandom device, the get_random_bytes function, and the get_random_{u8, - * u16,u32,u64,int,long} family of functions. + * u16,u32,u64,long} family of functions. * * Returns: true if the input pool has been seeded. * false if the input pool has not been seeded. @@ -161,15 +161,14 @@ EXPORT_SYMBOL(wait_for_random_bytes); * u16 get_random_u16() * u32 get_random_u32() * u64 get_random_u64() - * unsigned int get_random_int() * unsigned long get_random_long() * * These interfaces will return the requested number of random bytes * into the given buffer or as a return value. This is equivalent to - * a read from /dev/urandom. The u8, u16, u32, u64, int, and long - * family of functions may be higher performance for one-off random - * integers, because they do a bit of buffering and do not invoke - * reseeding until the buffer is emptied. + * a read from /dev/urandom. The u8, u16, u32, u64, long family of + * functions may be higher performance for one-off random integers, + * because they do a bit of buffering and do not invoke reseeding + * until the buffer is emptied. * *********************************************************************/ diff --git a/include/linux/prandom.h b/include/linux/prandom.h index 78db003bc290..e0a0759dd09c 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -12,18 +12,6 @@ #include #include -/* Deprecated: use get_random_u32 instead. */ -static inline u32 prandom_u32(void) -{ - return get_random_u32(); -} - -/* Deprecated: use get_random_bytes instead. */ -static inline void prandom_bytes(void *buf, size_t nbytes) -{ - return get_random_bytes(buf, nbytes); -} - struct rnd_state { __u32 s1, s2, s3, s4; }; diff --git a/include/linux/random.h b/include/linux/random.h index 08322f700cdc..147a5e0d0b8e 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -42,10 +42,6 @@ u8 get_random_u8(void); u16 get_random_u16(void); u32 get_random_u32(void); u64 get_random_u64(void); -static inline unsigned int get_random_int(void) -{ - return get_random_u32(); -} static inline unsigned long get_random_long(void) { #if BITS_PER_LONG == 64 @@ -100,7 +96,6 @@ declare_get_random_var_wait(u8, u8) declare_get_random_var_wait(u16, u16) 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