This is a note to let you know that I've just added the patch titled arm64: mte: Ensure the cleared tags are visible before setting the PTE to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm64-mte-ensure-the-cleared-tags-are-visible-before-setting-the-pte.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 1d0cb4c8864addc362bae98e8ffa5500c87e1227 Mon Sep 17 00:00:00 2001 From: Catalin Marinas <catalin.marinas@xxxxxxx> Date: Tue, 17 May 2022 10:35:32 +0100 Subject: arm64: mte: Ensure the cleared tags are visible before setting the PTE From: Catalin Marinas <catalin.marinas@xxxxxxx> 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@xxxxxxx> Fixes: 34bfeea4a9e9 ("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE") Cc: <stable@xxxxxxxxxxxxxxx> # 5.10.x Reported-by: Vladimir Murzin <vladimir.murzin@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Reviewed-by: Steven Price <steven.price@xxxxxxx> Tested-by: Vladimir Murzin <vladimir.murzin@xxxxxxx> Link: https://lore.kernel.org/r/20220517093532.127095-1-catalin.marinas@xxxxxxx Signed-off-by: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/mte.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -73,6 +73,9 @@ 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) Patches currently in stable-queue which might be from catalin.marinas@xxxxxxx are queue-5.15/arm64-mte-ensure-the-cleared-tags-are-visible-before-setting-the-pte.patch