From: Daniel Axtens <email@example.com> To: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Cc: firstname.lastname@example.org, email@example.com, Daniel Axtens <firstname.lastname@example.org> Subject: [PATCH v3 0/3] Fix some incompatibilites between KASAN and FORTIFY_SOURCE Date: Fri, 24 Apr 2020 01:45:00 +1000 [thread overview] Message-ID: <email@example.com> (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. v3: resend with Reviewed-bys, hopefully for inclusion in 5.8. 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:[~2020-04-23 15:45 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-23 15:45 Daniel Axtens [this message] 2020-04-23 15:45 ` [PATCH v3 1/3] kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE Daniel Axtens 2020-04-23 15:45 ` [PATCH v3 2/3] string.h: fix incompatibility between FORTIFY_SOURCE and KASAN Daniel Axtens 2020-04-23 15:45 ` [PATCH v3 3/3] kasan: initialise array in kasan_memcmp test Daniel Axtens 2020-04-23 17:25 ` Dmitry Vyukov 2020-04-24 14:37 ` Daniel Axtens 2020-04-24 6:54 ` [PATCH v3 0/3] Fix some incompatibilites between KASAN and FORTIFY_SOURCE David Gow
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