The patch titled
Subject: x86_64: increase stack size for KASAN_EXTRA
has been added to the -mm tree. Its filename is
x86_64-increase-stack-size-for-kasan_extra.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/x86_64-increase-stack-size-for-kasan_extra.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/x86_64-increase-stack-size-for-kasan_extra.patch
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------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: x86_64: increase stack size for KASAN_EXTRA
If the kernel is configured with KASAN_EXTRA, the stack size is increasted
significantly because this option sets "-fstack-reuse" to "none" in GCC
[1]. As a result, it triggers stack overrun quite often with 32k stack
size compiled using GCC 8. For example, this reproducer
https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/\
syscalls/madvise/madvise06.c
triggers a "corrupted stack end detected inside scheduler" very reliably
with CONFIG_SCHED_STACK_END_CHECK enabled.
There are just too many functions that could have a large stack with
KASAN_EXTRA due to large local variables that have been called over and
over again without being able to reuse the stacks. Some noticiable ones
are
size
7648 shrink_page_list
3584 xfs_rmap_convert
3312 migrate_page_move_mapping
3312 dev_ethtool
3200 migrate_misplaced_transhuge_page
3168 copy_process
There are other 49 functions are over 2k in size while compiling kernel
with "-Wframe-larger-than=" even with a related minimal config on this
machine. Hence, it is too much work to change Makefiles for each object
to compile without "-fsanitize-address-use-after-scope" individually.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715#c23
Although there is a patch in GCC 9 to help the situation, GCC 9 probably
won't be released in a few months and then it probably take another
6-month to 1-year for all major distros to include it as a default.
Hence, the stack usage with KASAN_EXTRA can be revisited again in 2020
when GCC 9 is everywhere. Until then, this patch will help users avoid
stack overrun.
This has already been fixed for arm64 for the same reason via
6e8830674ea ("arm64: kasan: Increase stack size for KASAN_EXTRA").
Link: http://lkml.kernel.org/r/20190109215209.2903-1-cai@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/page_64_types.h | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/x86/include/asm/page_64_types.h~x86_64-increase-stack-size-for-kasan_extra
+++ a/arch/x86/include/asm/page_64_types.h
@@ -7,7 +7,11 @@
#endif
#ifdef CONFIG_KASAN
+#ifdef CONFIG_KASAN_EXTRA
+#define KASAN_STACK_ORDER 2
+#else
#define KASAN_STACK_ORDER 1
+#endif
#else
#define KASAN_STACK_ORDER 0
#endif
_
Patches currently in -mm which might be from cai@xxxxxx are
mm-page_owner-fix-for-deferred-struct-page-init.patch
x86_64-increase-stack-size-for-kasan_extra.patch
page_poison-plays-nicely-with-kasan.patch
signal-allow-the-null-signal-in-rt_sigqueueinfo.patch
