From: Catalin Marinas catalin.marinas@arm.com
commit 1d0cb4c8864addc362bae98e8ffa5500c87e1227 upstream.
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: Catalin Marinas catalin.marinas@arm.com Fixes: 34bfeea4a9e9 ("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: Vladimir Murzin vladimir.murzin@arm.com Cc: Will Deacon will@kernel.org Reviewed-by: Steven Price steven.price@arm.com Tested-by: Vladimir Murzin vladimir.murzin@arm.com Link: https://lore.kernel.org/r/20220517093532.127095-1-catalin.marinas@arm.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/mte.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -76,6 +76,9 @@ void mte_sync_tags(pte_t old_pte, pte_t 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)