From: Vladimir Murzin <vladimir.murzin@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
Steven Price <steven.price@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: Re: [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE
Date: Tue, 17 May 2022 10:39:54 +0100 [thread overview]
Message-ID: <9d73e55a-4979-d304-238e-0b63dba5d8ee@arm.com> (raw)
In-Reply-To: <20220517093532.127095-1-catalin.marinas@arm.com>
On 5/17/22 10:35, Catalin Marinas wrote:
> 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>
> ---
>
> Changes in v2:
> - make the barrier unconditional
> - not including reviewed-by, tested-by tags for v1 as the patch is slightly
> different
>
> arch/arm64/kernel/mte.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 90994aca54f3..d565ae25e48f 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -67,6 +67,9 @@ 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)
As I said in another e-mail this version has been tested in parallel to v1, so
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Cheers
Vladimir
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next prev parent reply other threads:[~2022-05-17 9:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-17 9:35 [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE Catalin Marinas
2022-05-17 9:39 ` Vladimir Murzin [this message]
2022-05-17 10:23 ` Steven Price
2022-05-17 13:16 ` Vincenzo Frascino
2022-05-17 14:04 ` Will Deacon
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