kasan: remove use after scope bugs detection.
authorAndrey Ryabinin <aryabinin@virtuozzo.com>
Tue, 5 Mar 2019 23:41:20 +0000 (15:41 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 6 Mar 2019 05:07:13 +0000 (21:07 -0800)
commit7771bdbbfd3d6f204631b6fd9e1bbc30cd15918e
tree1f715a5317669f6473d1d4ddb4f5bf761e918e71
parent46612b751c4941c5c0472ddf04027e877ae5990f
kasan: remove use after scope bugs detection.

Use after scope bugs detector seems to be almost entirely useless for
the linux kernel.  It exists over two years, but I've seen only one
valid bug so far [1].  And the bug was fixed before it has been
reported.  There were some other use-after-scope reports, but they were
false-positives due to different reasons like incompatibility with
structleak plugin.

This feature significantly increases stack usage, especially with GCC <
9 version, and causes a 32K stack overflow.  It probably adds
performance penalty too.

Given all that, let's remove use-after-scope detector entirely.

While preparing this patch I've noticed that we mistakenly enable
use-after-scope detection for clang compiler regardless of
CONFIG_KASAN_EXTRA setting.  This is also fixed now.

[1] http://lkml.kernel.org/r/<20171129052106.rhgbjhhis53hkgfn@wfg-t540p.sh.intel.com>

Link: http://lkml.kernel.org/r/20190111185842.13978-1-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Will Deacon <will.deacon@arm.com> [arm64]
Cc: Qian Cai <cai@lca.pw>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
arch/arm64/include/asm/memory.h
lib/Kconfig.debug
lib/Kconfig.kasan
lib/test_kasan.c
mm/kasan/generic.c
mm/kasan/generic_report.c
mm/kasan/kasan.h
scripts/Makefile.kasan
scripts/gcc-plugins/Kconfig