When a huge page is split into normal pages, part of the head page flags
are transferred to the tail pages. However, the PG_arch_* flags are not
part of the preserved set.
PG_arch_2 is used by the arm64 MTE support to mark pages that have valid
tags. The absence of such flag would cause the arm64 set_pte_at() to
clear the tags in order to avoid stale tags exposed to user or the
swapping out hooks to ignore the tags. Not preserving PG_arch_2 on huge
page splitting leads to tag corruption in the tail pages.
Preserve the newly added PG_arch_2 flag in __split_huge_page_tail().
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Notes:
v7:
- Only preserve PG_arch_2 in __split_huge_page_tail(). The PG_arch_1
flag will be discussed separately as it may potentially impact s390
and x86.
New in v6.
mm/huge_memory.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2ccff8472cd4..1a5773c95f53 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2337,6 +2337,9 @@ static void __split_huge_page_tail(struct page *head, int tail,
(1L << PG_workingset) |
(1L << PG_locked) |
(1L << PG_unevictable) |
+#ifdef CONFIG_64BIT
+ (1L << PG_arch_2) |
+#endif
(1L << PG_dirty)));
/* ->mapping in first tail page is compound_mapcount */
