From: Qian Cai <cai@lca.pw>
To: akpm@linux-foundation.org
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org,
Qian Cai <cai@lca.pw>
Subject: [RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA
Date: Wed, 9 Jan 2019 16:52:09 -0500 [thread overview]
Message-ID: <20190109215209.2903-1-cai@lca.pw> (raw)
In-Reply-To: <20181228020639.80425-1-cai@lca.pw>
If the kernel is configured with KASAN_EXTRA, the stack size is
increasted significantly due to enable this option will set
"-fstack-reuse" to "none" in GCC [1]. As the results, it could trigger
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
could trigger 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).
Signed-off-by: Qian Cai <cai@lca.pw>
---
arch/x86/include/asm/page_64_types.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 8f657286d599..0ce558a8150d 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/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
--
2.17.2 (Apple Git-113)
next prev parent reply other threads:[~2019-01-09 21:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-28 2:06 [PATCH] x86_64: increase stack size for KASAN_EXTRA Qian Cai
2019-01-09 21:52 ` Qian Cai [this message]
2019-01-09 22:02 ` [RESEND PATCH] " Andrew Morton
2019-01-10 4:20 ` Qian Cai
2019-01-11 18:55 ` Andrey Ryabinin
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