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mm, kasan: use compare-exchange operation to set KASAN page tag

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commit 27fe73394a1c6d0b07fa4d95f1bca116d1cc66e9 upstream.

It has been reported that the tag setting operation on newly-allocated
pages can cause the page flags to be corrupted when performed
concurrently with other flag updates as a result of the use of
non-atomic operations.

Fix the problem by using a compare-exchange loop to update the tag.

Link: https://lkml.kernel.org/r/20220120020148.1632253-1-pcc@google.com
Link: https://linux-review.googlesource.com/id/I456b24a2b9067d93968d43b4bb3351c0cec63101
Fixes: 2813b9c029 ("kasan, mm, arm64: tag non slab memory allocated via pagealloc")
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Collingbourne
2022-01-29 13:41:14 -08:00
committed by Greg Kroah-Hartman
parent 28b346571e
commit 4ca8a0bc83
1 changed files with 12 additions and 5 deletions
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17
include/linux/mm.h
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@@ -1511,11 +1511,18 @@ static inline u8 page_kasan_tag(const struct page *page)
static inline void page_kasan_tag_set(struct page *page, u8 tag) static inline void page_kasan_tag_set(struct page *page, u8 tag)
{ {
if (kasan_enabled()) { unsigned long old_flags, flags;
tag ^= 0xff;
page->flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT); if (!kasan_enabled())
page->flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT; return;
}
tag ^= 0xff;
old_flags = READ_ONCE(page->flags);
do {
flags = old_flags;
flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT);
flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT;
} while (unlikely(!try_cmpxchg(&page->flags, &old_flags, flags)));
} }
static inline void page_kasan_tag_reset(struct page *page) static inline void page_kasan_tag_reset(struct page *page)