From c275c5c6d50a0518cdb0584e85905d10e7cefc6e Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Wed, 2 Jun 2021 16:52:30 -0700 Subject: kasan: disable freed user page poisoning with HW tags Poisoning freed pages protects against kernel use-after-free. The likelihood of such a bug involving kernel pages is significantly higher than that for user pages. At the same time, poisoning freed pages can impose a significant performance cost, which cannot always be justified for user pages given the lower probability of finding a bug. Therefore, disable freed user page poisoning when using HW tags. We identify "user" pages via the flag set GFP_HIGHUSER_MOVABLE, which indicates a strong likelihood of not being directly accessible to the kernel. Signed-off-by: Peter Collingbourne Reviewed-by: Andrey Konovalov Link: https://linux-review.googlesource.com/id/I716846e2de8ef179f44e835770df7e6307be96c9 Link: https://lore.kernel.org/r/20210602235230.3928842-5-pcc@google.com Signed-off-by: Will Deacon --- include/linux/page-flags.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/page-flags.h') diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 04a34c08e0a6..40e2c5000585 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -137,6 +137,9 @@ enum pageflags { #endif #ifdef CONFIG_64BIT PG_arch_2, +#endif +#ifdef CONFIG_KASAN_HW_TAGS + PG_skip_kasan_poison, #endif __NR_PAGEFLAGS, @@ -443,6 +446,12 @@ TESTCLEARFLAG(Young, young, PF_ANY) PAGEFLAG(Idle, idle, PF_ANY) #endif +#ifdef CONFIG_KASAN_HW_TAGS +PAGEFLAG(SkipKASanPoison, skip_kasan_poison, PF_HEAD) +#else +PAGEFLAG_FALSE(SkipKASanPoison) +#endif + /* * PageReported() is used to track reported free pages within the Buddy * allocator. We can use the non-atomic version of the test and set -- cgit v1.2.3