Code inspection reveals that PG_skip_kasan_poison is redundant with kasantag, because the former is intended to be set iff the latter is the match-all tag. It can also be observed that it's basically pointless to poison pages which have kasantag=0, because any pages with this tag would have been pointed to by pointers with match-all tags, so poisoning the pages would have little to no effect in terms of bug detection. Therefore, change the condition in should_skip_kasan_poison() to check kasantag instead, and remove PG_skip_kasan_poison. Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> Link: https://linux-review.googlesource.com/id/I57f825f2eaeaf7e8389d6cf4597c8a5821359838 --- I sent this independently of https://lore.kernel.org/all/20230224061550.177541-1-pcc@xxxxxxxxxx/ because I initially thought that the patches were independent. But moments after sending it, I realized that this patch depends on that one, because without that patch, this patch will end up disabling page poisoning altogether! But it's too late to turn them into a series now; I'll do that for v2. include/linux/page-flags.h | 9 --------- include/trace/events/mmflags.h | 9 +-------- mm/page_alloc.c | 28 ++++++++-------------------- 3 files changed, 9 insertions(+), 37 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index a7e3a3405520..74f81a52e7e1 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -135,9 +135,6 @@ enum pageflags { #ifdef CONFIG_ARCH_USES_PG_ARCH_X PG_arch_2, PG_arch_3, -#endif -#ifdef CONFIG_KASAN_HW_TAGS - PG_skip_kasan_poison, #endif __NR_PAGEFLAGS, @@ -594,12 +591,6 @@ 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, skip_kasan_poison) -#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 diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h index 9db52bc4ce19..c448694fc7e9 100644 --- a/include/trace/events/mmflags.h +++ b/include/trace/events/mmflags.h @@ -96,12 +96,6 @@ #define IF_HAVE_PG_ARCH_X(flag,string) #endif -#ifdef CONFIG_KASAN_HW_TAGS -#define IF_HAVE_PG_SKIP_KASAN_POISON(flag,string) ,{1UL << flag, string} -#else -#define IF_HAVE_PG_SKIP_KASAN_POISON(flag,string) -#endif - #define __def_pageflag_names \ {1UL << PG_locked, "locked" }, \ {1UL << PG_waiters, "waiters" }, \ @@ -130,8 +124,7 @@ IF_HAVE_PG_HWPOISON(PG_hwpoison, "hwpoison" ) \ IF_HAVE_PG_IDLE(PG_young, "young" ) \ IF_HAVE_PG_IDLE(PG_idle, "idle" ) \ IF_HAVE_PG_ARCH_X(PG_arch_2, "arch_2" ) \ -IF_HAVE_PG_ARCH_X(PG_arch_3, "arch_3" ) \ -IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison") +IF_HAVE_PG_ARCH_X(PG_arch_3, "arch_3" ) #define show_page_flags(flags) \ (flags) ? __print_flags(flags, "|", \ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7136c36c5d01..2509b8bde8d5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1380,7 +1380,7 @@ static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags) return deferred_pages_enabled() || (!IS_ENABLED(CONFIG_KASAN_GENERIC) && (fpi_flags & FPI_SKIP_KASAN_POISON)) || - PageSkipKASanPoison(page); + page_kasan_tag(page) == 0xff; } static void kernel_init_pages(struct page *page, int numpages) @@ -2511,22 +2511,13 @@ inline void post_alloc_hook(struct page *page, unsigned int order, /* Take note that memory was initialized by the loop above. */ init = false; } - if (!should_skip_kasan_unpoison(gfp_flags)) { - /* Try unpoisoning (or setting tags) and initializing memory. */ - if (kasan_unpoison_pages(page, order, init)) { - /* Take note that memory was initialized by KASAN. */ - if (kasan_has_integrated_init()) - init = false; - /* Take note that memory tags were set by KASAN. */ - reset_tags = false; - } else { - /* - * KASAN decided to exclude this allocation from being - * (un)poisoned due to sampling. Make KASAN skip - * poisoning when the allocation is freed. - */ - SetPageSkipKASanPoison(page); - } + if (!should_skip_kasan_unpoison(gfp_flags) && + kasan_unpoison_pages(page, order, init)) { + /* Take note that memory was initialized by KASAN. */ + if (kasan_has_integrated_init()) + init = false; + /* Take note that memory tags were set by KASAN. */ + reset_tags = false; } /* * If memory tags have not been set by KASAN, reset the page tags to @@ -2539,9 +2530,6 @@ inline void post_alloc_hook(struct page *page, unsigned int order, /* If memory is still not initialized, initialize it now. */ if (init) kernel_init_pages(page, 1 << order); - /* Propagate __GFP_SKIP_KASAN_POISON to page flags. */ - if (kasan_hw_tags_enabled() && (gfp_flags & __GFP_SKIP_KASAN_POISON)) - SetPageSkipKASanPoison(page); set_page_owner(page, order, gfp_flags); page_table_check_alloc(page, order); -- 2.39.2.637.g21b0678d19-goog
