Messages in this thread | | | Date | Wed, 9 Jan 2019 14:02:01 -0800 | From | Andrew Morton <> | Subject | Re: [RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA |
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On Wed, 9 Jan 2019 16:52:09 -0500 Qian Cai <cai@lca.pw> wrote:
> 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).
Sounds good.
> --- 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
I'm suspecting this logic could be performed in Kconfig, for all architectures. Add a new always-defined CONFIG_KASAN_STACK_ORDER?
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