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mm: kasan: Ensure the tags are visible before the tag in page->flags

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__kasan_unpoison_pages() colours the memory with a random tag and stores
it in page->flags in order to re-create the tagged pointer via
page_to_virt() later. When the tag from the page->flags is read, ensure
that the in-memory tags are already visible by re-ordering the
page_kasan_tag_set() after kasan_unpoison(). The former already has
barriers in place through try_cmpxchg(). On the reader side, the order
is ensured by the address dependency between page->flags and the memory
access.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20220610152141.2148929-2-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Catalin Marinas 2022-06-10 16:21:38 +01:00 committed by Will Deacon
parent a111daf0c5
commit ed0a6d1d97
1 changed files with 2 additions and 1 deletions
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3
mm/kasan/common.c
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@ -108,9 +108,10 @@ void __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
return;
tag = kasan_random_tag();
kasan_unpoison(set_tag(page_address(page), tag),
PAGE_SIZE << order, init);
for (i = 0; i < (1 << order); i++)
page_kasan_tag_set(page + i, tag);
kasan_unpoison(page_address(page), PAGE_SIZE << order, init);
}
void __kasan_poison_pages(struct page *page, unsigned int order, bool init)