diff options
| author | Peter Collingbourne <pcc@google.com> | 2021-06-03 02:52:30 +0300 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-06-04 21:32:21 +0300 |
| commit | c275c5c6d50a0518cdb0584e85905d10e7cefc6e (patch) | |
| tree | b621c3297979537bc51d124dbf57ebc932b98ca2 /mm | |
| parent | 013bb59dbb7cf876449df860946458a595a96d51 (diff) | |
| download | linux-c275c5c6d50a0518cdb0584e85905d10e7cefc6e.tar.xz | |
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 <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
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 <will@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/kasan/hw_tags.c | 3 | ||||
| -rw-r--r-- | mm/page_alloc.c | 12 |
2 files changed, 10 insertions, 5 deletions
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 41fd5326ee0a..ed5e5b833d61 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -246,6 +246,9 @@ void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags) */ bool init = !want_init_on_free() && want_init_on_alloc(flags); + if (flags & __GFP_SKIP_KASAN_POISON) + SetPageSkipKASanPoison(page); + if (flags & __GFP_ZEROTAGS) { int i; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 13937e793fda..5ad76e540a22 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -394,11 +394,12 @@ static DEFINE_STATIC_KEY_TRUE(deferred_pages); * on-demand allocation and then freed again before the deferred pages * initialization is done, but this is not likely to happen. */ -static inline bool should_skip_kasan_poison(fpi_t fpi_flags) +static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags) { return static_branch_unlikely(&deferred_pages) || (!IS_ENABLED(CONFIG_KASAN_GENERIC) && - (fpi_flags & FPI_SKIP_KASAN_POISON)); + (fpi_flags & FPI_SKIP_KASAN_POISON)) || + PageSkipKASanPoison(page); } /* Returns true if the struct page for the pfn is uninitialised */ @@ -449,10 +450,11 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn) return false; } #else -static inline bool should_skip_kasan_poison(fpi_t fpi_flags) +static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags) { return (!IS_ENABLED(CONFIG_KASAN_GENERIC) && - (fpi_flags & FPI_SKIP_KASAN_POISON)); + (fpi_flags & FPI_SKIP_KASAN_POISON)) || + PageSkipKASanPoison(page); } static inline bool early_page_uninitialised(unsigned long pfn) @@ -1244,7 +1246,7 @@ static __always_inline bool free_pages_prepare(struct page *page, unsigned int order, bool check_free, fpi_t fpi_flags) { int bad = 0; - bool skip_kasan_poison = should_skip_kasan_poison(fpi_flags); + bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags); VM_BUG_ON_PAGE(PageTail(page), page); |