Commit 72e6afa0 authored Jul 02, 2020 by Catalin Marinas

mm: Preserve the PG_arch_2 flag in __split_huge_page_tail()

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@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>

parent 4beba948

mm/huge_memory.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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 */

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