From: Catalin Marinas <catalin.marinas@xxxxxxx> [ Upstream commit ed0a6d1d973e9763989b44913ae1bd2a5d5d5777 ] __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@xxxxxxx> Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Link: https://lore.kernel.org/r/20220610152141.2148929-2-catalin.marinas@xxxxxxx Signed-off-by: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- mm/kasan/common.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 2baf121fb8c5..0c36d3df23f3 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -109,9 +109,10 @@ 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) -- 2.35.1
