4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 6e8830674ea77f57d57a33cca09083b117a71f41 ]
If the kernel is configured with KASAN_EXTRA, the stack size is increased significantly due to setting the GCC -fstack-reuse option to "none" [1]. As a result, it can trigger a 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/sysca...
can trigger a "corrupted stack end detected inside scheduler" very reliably with CONFIG_SCHED_STACK_END_CHECK enabled. There are other reports at:
https://lore.kernel.org/lkml/1542144497.12945.29.camel@gmx.us/ https://lore.kernel.org/lkml/721E7B42-2D55-4866-9C1A-3E8D64F33F9C@gmx.us/
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 7536 shrink_inactive_list 7440 shrink_page_list 6560 fscache_stats_show 3920 jbd2_journal_commit_transaction 3216 try_to_unmap_one 3072 migrate_page_move_mapping 3584 migrate_misplaced_transhuge_page 3920 ip_vs_lblcr_schedule 4304 lpfc_nvme_info_show 3888 lpfc_debugfs_nvmestat_data.constprop
There are other 49 functions over 2k in size while compiling kernel with "-Wframe-larger-than=" 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
Signed-off-by: Qian Cai cai@lca.pw Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/memory.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index f0a5c9531e8b..778af0b7f7fd 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -67,12 +67,17 @@ /* * KASAN requires 1/8th of the kernel virtual address space for the shadow * region. KASAN can bloat the stack significantly, so double the (minimum) - * stack size when KASAN is in use. + * stack size when KASAN is in use, and then double it again if KASAN_EXTRA is + * on. */ #ifdef CONFIG_KASAN #define KASAN_SHADOW_SCALE_SHIFT 3 #define KASAN_SHADOW_SIZE (UL(1) << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT)) +#ifdef CONFIG_KASAN_EXTRA +#define KASAN_THREAD_SHIFT 2 +#else #define KASAN_THREAD_SHIFT 1 +#endif /* CONFIG_KASAN_EXTRA */ #else #define KASAN_SHADOW_SIZE (0) #define KASAN_THREAD_SHIFT 0