From: Catalin Marinas catalin.marinas@arm.com
[ Upstream commit b98c94eed4a975e0c80b7e90a649a46967376f58 ]
The arm64 copy_highpage() assumes that the destination page is newly allocated and not MTE-tagged (PG_mte_tagged unset) and warns accordingly. However, following commit 060913999d7a ("mm: migrate: support poisoned recover from migrate folio"), folio_mc_copy() is called before __folio_migrate_mapping(). If the latter fails (-EAGAIN), the copy will be done again to the same destination page. Since copy_highpage() already set the PG_mte_tagged flag, this second copy will warn.
Replace the WARN_ON_ONCE(page already tagged) in the arm64 copy_highpage() with a comment.
Reported-by: syzbot+d1974fc28545a3e6218b@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/68dda1ae.a00a0220.102ee.0065.GAE@google.com Reviewed-by: David Hildenbrand david@redhat.com Cc: Will Deacon will@kernel.org Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: stable@vger.kernel.org # 6.12.x Reviewed-by: Yang Shi yang@os.amperecomputing.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com [ omitted hugetlb MTE changes ] Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/mm/copypage.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c index a7bb20055ce09..9e734d6314e03 100644 --- a/arch/arm64/mm/copypage.c +++ b/arch/arm64/mm/copypage.c @@ -25,8 +25,13 @@ void copy_highpage(struct page *to, struct page *from) page_kasan_tag_reset(to);
if (system_supports_mte() && page_mte_tagged(from)) { - /* It's a new page, shouldn't have been tagged yet */ - WARN_ON_ONCE(!try_page_mte_tagging(to)); + /* + * Most of the time it's a new page that shouldn't have been + * tagged yet. However, folio migration can end up reusing the + * same page without untagging it. Ignore the warning if the + * page is already tagged. + */ + try_page_mte_tagging(to); mte_copy_page_tags(kto, kfrom); set_page_mte_tagged(to); }