Commit 1d0cb4c8 authored by Catalin Marinas's avatar Catalin Marinas Committed by Will Deacon
Browse files

arm64: mte: Ensure the cleared tags are visible before setting the PTE 



As an optimisation, only pages mapped with PROT_MTE in user space have
the MTE tags zeroed. This is done lazily at the set_pte_at() time via
mte_sync_tags(). However, this function is missing a barrier and another
CPU may see the PTE updated before the zeroed tags are visible. Add an
smp_wmb() barrier if the mapping is Normal Tagged.

Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Fixes: 34bfeea4 ("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE")
Cc: <stable@vger.kernel.org> # 5.10.x
Reported-by: default avatarVladimir Murzin <vladimir.murzin@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Tested-by: default avatarVladimir Murzin <vladimir.murzin@arm.com>
Link: https://lore.kernel.org/r/20220517093532.127095-1-catalin.marinas@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent eb3d8ea3

arch/arm64/kernel/mte.c

+3 −0
Original line number Diff line number Diff line
@@ -76,6 +76,9 @@ void mte_sync_tags(pte_t old_pte, pte_t pte) 
			mte_sync_page_tags(page, old_pte, check_swap,

					   pte_is_tagged);

	}



	/* ensure the tags are visible before the PTE is set */

	smp_wmb();

}



int memcmp_pages(struct page *page1, struct page *page2)