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| author | Andrey Konovalov <andreyknvl@google.com> | 2023-01-24 21:35:26 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-02 22:33:29 -0800 |
| commit | 420ef683b5217338bc679c33fd9361b52f53a526 (patch) | |
| tree | d0a3990ce49fdf21c86b671c42d308d28693102b /mm/page_alloc.c | |
| parent | 2e126aa29007353f069c3bab5c2cf52d231cd3ae (diff) | |
| download | lwn-420ef683b5217338bc679c33fd9361b52f53a526.tar.gz lwn-420ef683b5217338bc679c33fd9361b52f53a526.zip | |
kasan: reset page tags properly with sampling
The implementation of page_alloc poisoning sampling assumed that
tag_clear_highpage resets page tags for __GFP_ZEROTAGS allocations.
However, this is no longer the case since commit 70c248aca9e7 ("mm: kasan:
Skip unpoisoning of user pages").
This leads to kernel crashes when MTE-enabled userspace mappings are used
with Hardware Tag-Based KASAN enabled.
Reset page tags for __GFP_ZEROTAGS allocations in post_alloc_hook().
Also clarify and fix related comments.
[andreyknvl@google.com: update comment]
Link: https://lkml.kernel.org/r/5dbd866714b4839069e2d8469ac45b60953db290.1674592780.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/24ea20c1b19c2b4b56cf9f5b354915f8dbccfc77.1674592496.git.andreyknvl@google.com
Fixes: 44383cef54c0 ("kasan: allow sampling page_alloc allocations for HW_TAGS")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reported-by: Peter Collingbourne <pcc@google.com>
Tested-by: Peter Collingbourne <pcc@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 717f12e83b85..5ebce58026f1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2476,7 +2476,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) && !should_skip_init(gfp_flags); bool zero_tags = init && (gfp_flags & __GFP_ZEROTAGS); - bool reset_tags = !zero_tags; + bool reset_tags = true; int i; set_page_private(page, 0); @@ -2503,7 +2503,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, * (which happens only when memory should be initialized as well). */ if (zero_tags) { - /* Initialize both memory and tags. */ + /* Initialize both memory and memory tags. */ for (i = 0; i != 1 << order; ++i) tag_clear_highpage(page + i); @@ -2521,14 +2521,15 @@ inline void post_alloc_hook(struct page *page, unsigned int order, } else { /* * KASAN decided to exclude this allocation from being - * poisoned due to sampling. Skip poisoning as well. + * (un)poisoned due to sampling. Make KASAN skip + * poisoning when the allocation is freed. */ SetPageSkipKASanPoison(page); } } /* - * If memory tags have not been set, reset the page tags to ensure - * page_address() dereferencing does not fault. + * If memory tags have not been set by KASAN, reset the page tags to + * ensure page_address() dereferencing does not fault. */ if (reset_tags) { for (i = 0; i != 1 << order; ++i) |