From: Daniel Axtens <dja@axtens.net>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kasan-dev@googlegroups.com
Cc: linux-s390@vger.kernel.org, linux-xtensa@linux-xtensa.org,
x86@kernel.org, linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, dvyukov@google.com,
Daniel Axtens <dja@axtens.net>
Subject: [PATCH v2 0/3] Fix some incompatibilites between KASAN and FORTIFY_SOURCE
Date: Thu, 16 Jan 2020 17:26:22 +1100 [thread overview]
Message-ID: <20200116062625.32692-1-dja@axtens.net> (raw)
3 KASAN self-tests fail on a kernel with both KASAN and FORTIFY_SOURCE:
memchr, memcmp and strlen. I have observed this on x86 and powerpc.
When FORTIFY_SOURCE is on, a number of functions are replaced with
fortified versions, which attempt to check the sizes of the
operands. However, these functions often directly invoke __builtin_foo()
once they have performed the fortify check.
This breaks things in 2 ways:
- the three function calls are technically dead code, and can be
eliminated. When __builtin_ versions are used, the compiler can detect
this.
- Using __builtins may bypass KASAN checks if the compiler decides to
inline it's own implementation as sequence of instructions, rather than
emit a function call that goes out to a KASAN-instrumented
implementation.
The patches address each reason in turn. Finally, test_memcmp used a
stack array without explicit initialisation, which can sometimes break
too, so fix that up.
v2: - some cleanups, don't mess with arch code as I missed some wrinkles.
- add stack array init (patch 3)
Daniel Axtens (3):
kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE
string.h: fix incompatibility between FORTIFY_SOURCE and KASAN
kasan: initialise array in kasan_memcmp test
include/linux/string.h | 60 +++++++++++++++++++++++++++++++++---------
lib/test_kasan.c | 32 +++++++++++++---------
2 files changed, 68 insertions(+), 24 deletions(-)
--
2.20.1
next reply other threads:[~2020-01-16 6:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 6:26 Daniel Axtens [this message]
2020-01-16 6:26 ` [PATCH v2 1/3] kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE Daniel Axtens
2020-01-16 6:26 ` [PATCH v2 2/3] string.h: fix incompatibility between FORTIFY_SOURCE and KASAN Daniel Axtens
2020-01-16 8:11 ` Dmitry Vyukov
2020-01-16 6:26 ` [PATCH v2 3/3] kasan: initialise array in kasan_memcmp test Daniel Axtens
2020-01-16 8:07 ` Dmitry Vyukov
2020-02-26 23:48 ` [PATCH v2 0/3] Fix some incompatibilites between KASAN and FORTIFY_SOURCE Daniel Axtens
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