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. Also, See other bug reports, https://lore.kernel.org/lkml/1542144497.12945.29.camel@xxxxxx/ https://lore.kernel.org/lkml/721E7B42-2D55-4866-9C1A-3E8D64F33F9C@xxxxxx/ 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 are 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@xxxxxx> --- 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 b96442960aea..56562ff01076 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -76,12 +76,17 @@ /* * 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 -- 2.17.2 (Apple Git-113)
