The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 27fe73394a1c6d0b07fa4d95f1bca116d1cc66e9 Mon Sep 17 00:00:00 2001 From: Peter Collingbourne pcc@google.com Date: Sat, 29 Jan 2022 13:41:14 -0800 Subject: [PATCH] mm, kasan: use compare-exchange operation to set KASAN page tag
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/I456b24a2b9067d93968d43b4bb3351c0ce... Fixes: 2813b9c02962 ("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
diff --git a/include/linux/mm.h b/include/linux/mm.h index e1a84b1e6787..213cc569b192 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1506,11 +1506,18 @@ static inline u8 page_kasan_tag(const struct page *page)
static inline void page_kasan_tag_set(struct page *page, u8 tag) { - if (kasan_enabled()) { - tag ^= 0xff; - page->flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT); - page->flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT; - } + unsigned long old_flags, flags; + + if (!kasan_enabled()) + 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)