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authorAndrey Ryabinin <aryabinin@virtuozzo.com>2019-03-05 15:41:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-05 21:07:13 -0800
commit7771bdbbfd3d6f204631b6fd9e1bbc30cd15918e (patch)
tree1f715a5317669f6473d1d4ddb4f5bf761e918e71 /lib
parent46612b751c4941c5c0472ddf04027e877ae5990f (diff)
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>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug1
-rw-r--r--lib/Kconfig.kasan10
-rw-r--r--lib/test_kasan.c24
3 files changed, 0 insertions, 35 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d4df5b24d75e..a219f3488ad7 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -222,7 +222,6 @@ config ENABLE_MUST_CHECK
config FRAME_WARN
int "Warn for stack frames larger than (needs gcc 4.4)"
range 0 8192
- default 3072 if KASAN_EXTRA
default 2048 if GCC_PLUGIN_LATENT_ENTROPY
default 1280 if (!64BIT && PARISC)
default 1024 if (!64BIT && !PARISC)
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 9737059ec58b..9950b660e62d 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -78,16 +78,6 @@ config KASAN_SW_TAGS
endchoice
-config KASAN_EXTRA
- bool "KASAN: extra checks"
- depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST
- help
- This enables further checks in generic KASAN, for now it only
- includes the address-use-after-scope check that can lead to
- excessive kernel stack usage, frame size warnings and longer
- compile time.
- See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715
-
choice
prompt "Instrumentation type"
depends on KASAN
diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 51b78405bf24..7de2702621dc 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -480,29 +480,6 @@ static noinline void __init copy_user_test(void)
kfree(kmem);
}
-static noinline void __init use_after_scope_test(void)
-{
- volatile char *volatile p;
-
- pr_info("use-after-scope on int\n");
- {
- int local = 0;
-
- p = (char *)&local;
- }
- p[0] = 1;
- p[3] = 1;
-
- pr_info("use-after-scope on array\n");
- {
- char local[1024] = {0};
-
- p = local;
- }
- p[0] = 1;
- p[1023] = 1;
-}
-
static noinline void __init kasan_alloca_oob_left(void)
{
volatile int i = 10;
@@ -682,7 +659,6 @@ static int __init kmalloc_tests_init(void)
kasan_alloca_oob_right();
ksize_unpoisons_memory();
copy_user_test();
- use_after_scope_test();
kmem_cache_double_free();
kmem_cache_invalid_free();
kasan_memchr();