<feed xmlns='http://www.w3.org/2005/Atom'>
<title>user/sven/linux.git/lib, branch v4.4.148</title>
<subtitle>Linux Kernel
</subtitle>
<id>https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v4.4.148</id>
<link rel='self' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v4.4.148'/>
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<updated>2018-07-25T08:18:16Z</updated>
<entry>
<title>lib/rhashtable: consider param-&gt;min_size when setting initial table size</title>
<updated>2018-07-25T08:18:16Z</updated>
<author>
<name>Davidlohr Bueso</name>
<email>dave@stgolabs.net</email>
</author>
<published>2018-07-16T20:26:13Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=b67a684222441668cf326427d02c34a8dfedb6be'/>
<id>urn:sha1:b67a684222441668cf326427d02c34a8dfedb6be</id>
<content type='text'>
[ Upstream commit 107d01f5ba10f4162c38109496607eb197059064 ]

rhashtable_init() currently does not take into account the user-passed
min_size parameter unless param-&gt;nelem_hint is set as well. As such,
the default size (number of buckets) will always be HASH_DEFAULT_SIZE
even if the smallest allowed size is larger than that. Remediate this
by unconditionally calling into rounded_hashtable_size() and handling
things accordingly.

Signed-off-by: Davidlohr Bueso &lt;dbueso@suse.de&gt;
Acked-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>x86/cpufeature: Carve out X86_FEATURE_*</title>
<updated>2018-07-17T09:31:44Z</updated>
<author>
<name>Borislav Petkov</name>
<email>bp@suse.de</email>
</author>
<published>2018-07-14T09:26:52Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=7b2330a33983f103327f929189ef9c8f935d9f0c'/>
<id>urn:sha1:7b2330a33983f103327f929189ef9c8f935d9f0c</id>
<content type='text'>
commit cd4d09ec6f6c12a2cc3db5b7d8876a325a53545b upstream

Move them to a separate header and have the following
dependency:

  x86/cpufeatures.h &lt;- x86/processor.h &lt;- x86/cpufeature.h

This makes it easier to use the header in asm code and not
include the whole cpufeature.h and add guards for asm.

Suggested-by: H. Peter Anvin &lt;hpa@zytor.com&gt;
Signed-off-by: Borislav Petkov &lt;bp@suse.de&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Link: http://lkml.kernel.org/r/1453842730-28463-5-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Signed-off-by: Srivatsa S. Bhat &lt;srivatsa@csail.mit.edu&gt;
Reviewed-by: Matt Helsley (VMware) &lt;matt.helsley@gmail.com&gt;
Reviewed-by: Alexey Makhalov &lt;amakhalov@vmware.com&gt;
Reviewed-by: Bo Gan &lt;ganb@vmware.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>x86/headers: Don't include asm/processor.h in asm/atomic.h</title>
<updated>2018-07-17T09:31:44Z</updated>
<author>
<name>Andi Kleen</name>
<email>ak@linux.intel.com</email>
</author>
<published>2018-07-14T09:26:43Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=4307cf43911180477e15c6f1cceed0460428efae'/>
<id>urn:sha1:4307cf43911180477e15c6f1cceed0460428efae</id>
<content type='text'>
commit 153a4334c439cfb62e1d31cee0c790ba4157813d upstream

asm/atomic.h doesn't really need asm/processor.h anymore. Everything
it uses has moved to other header files. So remove that include.

processor.h is a nasty header that includes lots of
other headers and makes it prone to include loops. Removing the
include here makes asm/atomic.h a "leaf" header that can
be safely included in most other headers.

The only fallout is in the lib/atomic tester which relied on
this implicit include. Give it an explicit include.
(the include is in ifdef because the user is also in ifdef)

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Cc: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Cc: Jiri Olsa &lt;jolsa@redhat.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Mike Galbraith &lt;efault@gmx.de&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Stephane Eranian &lt;eranian@google.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Vince Weaver &lt;vincent.weaver@maine.edu&gt;
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1449018060-1742-1-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Signed-off-by: Srivatsa S. Bhat &lt;srivatsa@csail.mit.edu&gt;
Reviewed-by: Matt Helsley (VMware) &lt;matt.helsley@gmail.com&gt;
Reviewed-by: Alexey Makhalov &lt;amakhalov@vmware.com&gt;
Reviewed-by: Bo Gan &lt;ganb@vmware.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>lib/vsprintf: Remove atomic-unsafe support for %pCr</title>
<updated>2018-07-03T09:21:27Z</updated>
<author>
<name>Geert Uytterhoeven</name>
<email>geert+renesas@glider.be</email>
</author>
<published>2018-06-01T09:28:22Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=ddb54306acf482c8eb0beb4fb4e80d4b035d9e53'/>
<id>urn:sha1:ddb54306acf482c8eb0beb4fb4e80d4b035d9e53</id>
<content type='text'>
commit 666902e42fd8344b923c02dc5b0f37948ff4f225 upstream.

"%pCr" formats the current rate of a clock, and calls clk_get_rate().
The latter obtains a mutex, hence it must not be called from atomic
context.

Remove support for this rarely-used format, as vsprintf() (and e.g.
printk()) must be callable from any context.

Any remaining out-of-tree users will start seeing the clock's name
printed instead of its rate.

Reported-by: Jia-Ju Bai &lt;baijiaju1990@gmail.com&gt;
Fixes: 900cca2944254edd ("lib/vsprintf: add %pC{,n,r} format specifiers for clocks")
Link: http://lkml.kernel.org/r/1527845302-12159-5-git-send-email-geert+renesas@glider.be
To: Jia-Ju Bai &lt;baijiaju1990@gmail.com&gt;
To: Jonathan Corbet &lt;corbet@lwn.net&gt;
To: Michael Turquette &lt;mturquette@baylibre.com&gt;
To: Stephen Boyd &lt;sboyd@kernel.org&gt;
To: Zhang Rui &lt;rui.zhang@intel.com&gt;
To: Eduardo Valentin &lt;edubezval@gmail.com&gt;
To: Eric Anholt &lt;eric@anholt.net&gt;
To: Stefan Wahren &lt;stefan.wahren@i2se.com&gt;
To: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Sergey Senozhatsky &lt;sergey.senozhatsky.work@gmail.com&gt;
Cc: Petr Mladek &lt;pmladek@suse.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Steven Rostedt &lt;rostedt@goodmis.org&gt;
Cc: linux-doc@vger.kernel.org
Cc: linux-clk@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-renesas-soc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Geert Uytterhoeven &lt;geert+renesas@glider.be&gt;
Cc: stable@vger.kernel.org # 4.1+
Signed-off-by: Geert Uytterhoeven &lt;geert+renesas@glider.be&gt;
Signed-off-by: Petr Mladek &lt;pmladek@suse.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y</title>
<updated>2018-05-30T05:48:56Z</updated>
<author>
<name>Yonghong Song</name>
<email>yhs@fb.com</email>
</author>
<published>2018-02-03T06:37:15Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=e7260c8fb01681591d19826edc8fe4b36b2ef0bf'/>
<id>urn:sha1:e7260c8fb01681591d19826edc8fe4b36b2ef0bf</id>
<content type='text'>
[ Upstream commit 09584b406742413ac4c8d7e030374d4daa045b69 ]

With CONFIG_BPF_JIT_ALWAYS_ON is defined in the config file,
tools/testing/selftests/bpf/test_kmod.sh failed like below:
  [root@localhost bpf]# ./test_kmod.sh
  sysctl: setting key "net.core.bpf_jit_enable": Invalid argument
  [ JIT enabled:0 hardened:0 ]
  [  132.175681] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
  [  132.458834] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
  [ JIT enabled:1 hardened:0 ]
  [  133.456025] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
  [  133.730935] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
  [ JIT enabled:1 hardened:1 ]
  [  134.769730] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
  [  135.050864] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
  [ JIT enabled:1 hardened:2 ]
  [  136.442882] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
  [  136.821810] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
  [root@localhost bpf]#

The test_kmod.sh load/remove test_bpf.ko multiple times with different
settings for sysctl net.core.bpf_jit_{enable,harden}. The failed test #297
of test_bpf.ko is designed such that JIT always fails.

Commit 290af86629b2 (bpf: introduce BPF_JIT_ALWAYS_ON config)
introduced the following tightening logic:
    ...
        if (!bpf_prog_is_dev_bound(fp-&gt;aux)) {
                fp = bpf_int_jit_compile(fp);
    #ifdef CONFIG_BPF_JIT_ALWAYS_ON
                if (!fp-&gt;jited) {
                        *err = -ENOTSUPP;
                        return fp;
                }
    #endif
    ...
With this logic, Test #297 always gets return value -ENOTSUPP
when CONFIG_BPF_JIT_ALWAYS_ON is defined, causing the test failure.

This patch fixed the failure by marking Test #297 as expected failure
when CONFIG_BPF_JIT_ALWAYS_ON is defined.

Fixes: 290af86629b2 (bpf: introduce BPF_JIT_ALWAYS_ON config)
Signed-off-by: Yonghong Song &lt;yhs@fb.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Signed-off-by: Sasha Levin &lt;alexander.levin@microsoft.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>kobject: don't use WARN for registration failures</title>
<updated>2018-05-02T14:53:42Z</updated>
<author>
<name>Dmitry Vyukov</name>
<email>dvyukov@google.com</email>
</author>
<published>2018-04-11T15:22:43Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=abb841c5e943316bbf74ddb27d188813b3cba0d9'/>
<id>urn:sha1:abb841c5e943316bbf74ddb27d188813b3cba0d9</id>
<content type='text'>
commit 3e14c6abbfb5c94506edda9d8e2c145d79375798 upstream.

This WARNING proved to be noisy. The function still returns an error
and callers should handle it. That's how most of kernel code works.
Downgrade the WARNING to pr_err() and leave WARNINGs for kernel bugs.

Signed-off-by: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Reported-by: syzbot+209c0f67f99fec8eb14b@syzkaller.appspotmail.com
Reported-by: syzbot+7fb6d9525a4528104e05@syzkaller.appspotmail.com
Reported-by: syzbot+2e63711063e2d8f9ea27@syzkaller.appspotmail.com
Reported-by: syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>x86/hweight: Get rid of the special calling convention</title>
<updated>2018-04-24T07:32:04Z</updated>
<author>
<name>Borislav Petkov</name>
<email>bp@suse.de</email>
</author>
<published>2016-05-30T10:56:27Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=c597f98755e0387067127033eef7a21a34ecf21c'/>
<id>urn:sha1:c597f98755e0387067127033eef7a21a34ecf21c</id>
<content type='text'>
commit f5967101e9de12addcda4510dfbac66d7c5779c3 upstream.

People complained about ARCH_HWEIGHT_CFLAGS and how it throws a wrench
into kcov, lto, etc, experimentations.

Add asm versions for __sw_hweight{32,64}() and do explicit saving and
restoring of clobbered registers. This gets rid of the special calling
convention. We get to call those functions on !X86_FEATURE_POPCNT CPUs.

We still need to hardcode POPCNT and register operands as some old gas
versions which we support, do not know about POPCNT.

Btw, remove redundant REX prefix from 32-bit POPCNT because alternatives
can do padding now.

Suggested-by: H. Peter Anvin &lt;hpa@zytor.com&gt;
Signed-off-by: Borislav Petkov &lt;bp@suse.de&gt;
Acked-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Link: http://lkml.kernel.org/r/1464605787-20603-1-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Signed-off-by: Matthias Kaehlcke &lt;mka@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>mm/vmalloc: add interfaces to free unmapped page table</title>
<updated>2018-03-28T16:40:14Z</updated>
<author>
<name>Toshi Kani</name>
<email>toshi.kani@hpe.com</email>
</author>
<published>2018-03-22T23:17:20Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=31895cfd79564111cdd5a9f48c5d491ae26a238e'/>
<id>urn:sha1:31895cfd79564111cdd5a9f48c5d491ae26a238e</id>
<content type='text'>
commit b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e upstream.

On architectures with CONFIG_HAVE_ARCH_HUGE_VMAP set, ioremap() may
create pud/pmd mappings.  A kernel panic was observed on arm64 systems
with Cortex-A75 in the following steps as described by Hanjun Guo.

 1. ioremap a 4K size, valid page table will build,
 2. iounmap it, pte0 will set to 0;
 3. ioremap the same address with 2M size, pgd/pmd is unchanged,
    then set the a new value for pmd;
 4. pte0 is leaked;
 5. CPU may meet exception because the old pmd is still in TLB,
    which will lead to kernel panic.

This panic is not reproducible on x86.  INVLPG, called from iounmap,
purges all levels of entries associated with purged address on x86.  x86
still has memory leak.

The patch changes the ioremap path to free unmapped page table(s) since
doing so in the unmap path has the following issues:

 - The iounmap() path is shared with vunmap(). Since vmap() only
   supports pte mappings, making vunmap() to free a pte page is an
   overhead for regular vmap users as they do not need a pte page freed
   up.

 - Checking if all entries in a pte page are cleared in the unmap path
   is racy, and serializing this check is expensive.

 - The unmap path calls free_vmap_area_noflush() to do lazy TLB purges.
   Clearing a pud/pmd entry before the lazy TLB purges needs extra TLB
   purge.

Add two interfaces, pud_free_pmd_page() and pmd_free_pte_page(), which
clear a given pud/pmd entry and free up a page for the lower level
entries.

This patch implements their stub functions on x86 and arm64, which work
as workaround.

[akpm@linux-foundation.org: fix typo in pmd_free_pte_page() stub]
Link: http://lkml.kernel.org/r/20180314180155.19492-2-toshi.kani@hpe.com
Fixes: e61ce6ade404e ("mm: change ioremap to set up huge I/O mappings")
Reported-by: Lei Li &lt;lious.lilei@hisilicon.com&gt;
Signed-off-by: Toshi Kani &lt;toshi.kani@hpe.com&gt;
Cc: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Wang Xuefeng &lt;wxf.wang@hisilicon.com&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Cc: Hanjun Guo &lt;guohanjun@huawei.com&gt;
Cc: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: "H. Peter Anvin" &lt;hpa@zytor.com&gt;
Cc: Borislav Petkov &lt;bp@suse.de&gt;
Cc: Matthew Wilcox &lt;willy@infradead.org&gt;
Cc: Chintan Pandya &lt;cpandya@codeaurora.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
[ tweak arm64 portion to rely on CONFIG_ARCH_HAVE_HUGE_VMAP - gregkh]
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>lib/mpi: Fix umul_ppmm() for MIPS64r6</title>
<updated>2018-03-03T09:19:42Z</updated>
<author>
<name>James Hogan</name>
<email>jhogan@kernel.org</email>
</author>
<published>2017-12-05T23:31:35Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=0db6b1db4f27f1a9f42c37579aee125334ce702e'/>
<id>urn:sha1:0db6b1db4f27f1a9f42c37579aee125334ce702e</id>
<content type='text'>
[ Upstream commit bbc25bee37d2b32cf3a1fab9195b6da3a185614a ]

Current MIPS64r6 toolchains aren't able to generate efficient
DMULU/DMUHU based code for the C implementation of umul_ppmm(), which
performs an unsigned 64 x 64 bit multiply and returns the upper and
lower 64-bit halves of the 128-bit result. Instead it widens the 64-bit
inputs to 128-bits and emits a __multi3 intrinsic call to perform a 128
x 128 multiply. This is both inefficient, and it results in a link error
since we don't include __multi3 in MIPS linux.

For example commit 90a53e4432b1 ("cfg80211: implement regdb signature
checking") merged in v4.15-rc1 recently broke the 64r6_defconfig and
64r6el_defconfig builds by indirectly selecting MPILIB. The same build
errors can be reproduced on older kernels by enabling e.g. CRYPTO_RSA:

lib/mpi/generic_mpih-mul1.o: In function `mpihelp_mul_1':
lib/mpi/generic_mpih-mul1.c:50: undefined reference to `__multi3'
lib/mpi/generic_mpih-mul2.o: In function `mpihelp_addmul_1':
lib/mpi/generic_mpih-mul2.c:49: undefined reference to `__multi3'
lib/mpi/generic_mpih-mul3.o: In function `mpihelp_submul_1':
lib/mpi/generic_mpih-mul3.c:49: undefined reference to `__multi3'
lib/mpi/mpih-div.o In function `mpihelp_divrem':
lib/mpi/mpih-div.c:205: undefined reference to `__multi3'
lib/mpi/mpih-div.c:142: undefined reference to `__multi3'

Therefore add an efficient MIPS64r6 implementation of umul_ppmm() using
inline assembly and the DMULU/DMUHU instructions, to prevent __multi3
calls being emitted.

Fixes: 7fd08ca58ae6 ("MIPS: Add build support for the MIPS R6 ISA")
Signed-off-by: James Hogan &lt;jhogan@kernel.org&gt;
Cc: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Cc: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Cc: "David S. Miller" &lt;davem@davemloft.net&gt;
Cc: linux-mips@linux-mips.org
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: Sasha Levin &lt;alexander.levin@microsoft.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>kasan: rework Kconfig settings</title>
<updated>2018-02-25T10:03:52Z</updated>
<author>
<name>Arnd Bergmann</name>
<email>arnd@arndb.de</email>
</author>
<published>2018-02-20T11:55:09Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=0ffa39fb594e22e974da2101d92d8967a7777253'/>
<id>urn:sha1:0ffa39fb594e22e974da2101d92d8967a7777253</id>
<content type='text'>
commit e7c52b84fb18f08ce49b6067ae6285aca79084a8 upstream.

We get a lot of very large stack frames using gcc-7.0.1 with the default
-fsanitize-address-use-after-scope --param asan-stack=1 options, which can
easily cause an overflow of the kernel stack, e.g.

  drivers/gpu/drm/i915/gvt/handlers.c:2434:1: warning: the frame size of 46176 bytes is larger than 3072 bytes
  drivers/net/wireless/ralink/rt2x00/rt2800lib.c:5650:1: warning: the frame size of 23632 bytes is larger than 3072 bytes
  lib/atomic64_test.c:250:1: warning: the frame size of 11200 bytes is larger than 3072 bytes
  drivers/gpu/drm/i915/gvt/handlers.c:2621:1: warning: the frame size of 9208 bytes is larger than 3072 bytes
  drivers/media/dvb-frontends/stv090x.c:3431:1: warning: the frame size of 6816 bytes is larger than 3072 bytes
  fs/fscache/stats.c:287:1: warning: the frame size of 6536 bytes is larger than 3072 bytes

To reduce this risk, -fsanitize-address-use-after-scope is now split out
into a separate CONFIG_KASAN_EXTRA Kconfig option, leading to stack
frames that are smaller than 2 kilobytes most of the time on x86_64.  An
earlier version of this patch also prevented combining KASAN_EXTRA with
KASAN_INLINE, but that is no longer necessary with gcc-7.0.1.

All patches to get the frame size below 2048 bytes with CONFIG_KASAN=y
and CONFIG_KASAN_EXTRA=n have been merged by maintainers now, so we can
bring back that default now.  KASAN_EXTRA=y still causes lots of
warnings but now defaults to !COMPILE_TEST to disable it in
allmodconfig, and it remains disabled in all other defconfigs since it
is a new option.  I arbitrarily raise the warning limit for KASAN_EXTRA
to 3072 to reduce the noise, but an allmodconfig kernel still has around
50 warnings on gcc-7.

I experimented a bit more with smaller stack frames and have another
follow-up series that reduces the warning limit for 64-bit architectures
to 1280 bytes (without CONFIG_KASAN).

With earlier versions of this patch series, I also had patches to address
the warnings we get with KASAN and/or KASAN_EXTRA, using a
"noinline_if_stackbloat" annotation.

That annotation now got replaced with a gcc-8 bugfix (see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715) and a workaround for
older compilers, which means that KASAN_EXTRA is now just as bad as
before and will lead to an instant stack overflow in a few extreme
cases.

This reverts parts of commit 3f181b4d8652 ("lib/Kconfig.debug: disable
-Wframe-larger-than warnings with KASAN=y").  Two patches in linux-next
should be merged first to avoid introducing warnings in an allmodconfig
build:
  3cd890dbe2a4 ("media: dvb-frontends: fix i2c access helpers for KASAN")
  16c3ada89cff ("media: r820t: fix r820t_write_reg for KASAN")

Do we really need to backport this?

I think we do: without this patch, enabling KASAN will lead to
unavoidable kernel stack overflow in certain device drivers when built
with gcc-7 or higher on linux-4.10+ or any version that contains a
backport of commit c5caf21ab0cf8.  Most people are probably still on
older compilers, but it will get worse over time as they upgrade their
distros.

The warnings we get on kernels older than this should all be for code
that uses dangerously large stack frames, though most of them do not
cause an actual stack overflow by themselves.The asan-stack option was
added in linux-4.0, and commit 3f181b4d8652 ("lib/Kconfig.debug:
disable -Wframe-larger-than warnings with KASAN=y") effectively turned
off the warning for allmodconfig kernels, so I would like to see this
fix backported to any kernels later than 4.0.

I have done dozens of fixes for individual functions with stack frames
larger than 2048 bytes with asan-stack, and I plan to make sure that
all those fixes make it into the stable kernels as well (most are
already there).

Part of the complication here is that asan-stack (from 4.0) was
originally assumed to always require much larger stacks, but that
turned out to be a combination of multiple gcc bugs that we have now
worked around and fixed, but sanitize-address-use-after-scope (from
v4.10) has a much higher inherent stack usage and also suffers from at
least three other problems that we have analyzed but not yet fixed
upstream, each of them makes the stack usage more severe than it should
be.

Link: http://lkml.kernel.org/r/20171221134744.2295529-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Acked-by: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Cc: Mauro Carvalho Chehab &lt;mchehab@kernel.org&gt;
Cc: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Cc: Andrey Konovalov &lt;andreyknvl@google.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
[arnd: rebase to v4.4; only re-enable warning]
Signed-off-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
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