Re: Patch "x86_64: increase stack size for KASAN_EXTRA" has been added to the 4.20-stable tree
On Thu, Feb 21, 2019 at 12:43:23AM -0500, Sasha Levin wrote:
> This is a note to let you know that I've just added the patch titled
>
> x86_64: increase stack size for KASAN_EXTRA
>
> to the 4.20-stable tree which can be found at:
>
> http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
>
> The filename of the patch is:
> x86_64-increase-stack-size-for-kasan_extra.patch
> and it can be found in the queue-4.20 subdirectory.
>
> If you, or anyone else, feels it should not be added to the stable tree,
> please let know about it.
>
>
>
> commit 67fd2fd35761d6bb8dcebe5070960c2f0baaef69
> Author: Qian Cai
> Date: Fri Feb 1 14:20:20 2019 -0800
>
> x86_64: increase stack size for KASAN_EXTRA
>
> [ Upstream commit a8e911d13540487942d53137c156bd7707f66e5d ]
>
> 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-...@lca.pw
> Signed-off-by: Qian Cai
> Cc: Thomas Gleixner
> Cc: Ingo Molnar
> Cc: Borislav Petkov
> Cc: "H. Peter Anvin"
> Cc: Andrey Ryabinin
> Cc: Alexander Potapenko
> Cc: Dmitry Vyukov
> Signed-off-by: Andrew Morton
> Signed-off-by: Linus Torvalds
> Signed-off-by: Sasha Levin
>
> diff --git a/arch/x86/include/asm/page_64_types.h
> b/arch/x86/include/asm/page_64_types.h
> index 8f657286d599a..0ce558a8150d3 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
This looks like it is also relevant for 4.19.y so I have queued it up
there too.
greg k-h
Re: [RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA
On 1/10/19 12:52 AM, Qian Cai 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). > > Signed-off-by: Qian Cai > --- > 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 So the kernel stack becomes 4-order page. That's above PAGE_ALLOC_COSTLY_ORDER, so people will start seeing fork() failures with -ENOMEM due to high memory fragmentation. I don't think we can afford such change. Give that use-after-scope has proven to be almost useless for the kernel, I think we should just remove it entirely. > +#else > #define KASAN_STACK_ORDER 1 > +#endif > #else > #define KASAN_STACK_ORDER 0 > #endif >
Re: [RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA
On 1/9/19 5:02 PM, Andrew Morton wrote: >> --- 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? > Sounds doable, but KASAN only support x86_64, arm64, s390 and xtensa so far. I am not sure I care about the later two nor I have any way to test them if they suffer the same problem. I'll keep looking if more arches start to implement KASAN, and then might be a good time to reduce all those code duplication.
Re: [RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA
On Wed, 9 Jan 2019 16:52:09 -0500 Qian Cai 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?
[RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA
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 --- 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)
[PATCH] x86_64: increase stack size for KASAN_EXTRA
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 --- 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)
