* [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE
@ 2022-05-17 9:35 Catalin Marinas
2022-05-17 9:39 ` Vladimir Murzin
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: Catalin Marinas @ 2022-05-17 9:35 UTC (permalink / raw)
To: Will Deacon
Cc: linux-arm-kernel, Steven Price, Vincenzo Frascino, Vladimir Murzin
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)
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE
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
2022-05-17 10:23 ` Steven Price
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Vladimir Murzin @ 2022-05-17 9:39 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon
Cc: linux-arm-kernel, Steven Price, Vincenzo Frascino
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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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE
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
@ 2022-05-17 10:23 ` Steven Price
2022-05-17 13:16 ` Vincenzo Frascino
2022-05-17 14:04 ` Will Deacon
3 siblings, 0 replies; 5+ messages in thread
From: Steven Price @ 2022-05-17 10:23 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon
Cc: linux-arm-kernel, Vincenzo Frascino, Vladimir Murzin
On 17/05/2022 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>
Reviewed-by: Steven Price <steven.price@arm.com>
> ---
>
> 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)
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE
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
2022-05-17 10:23 ` Steven Price
@ 2022-05-17 13:16 ` Vincenzo Frascino
2022-05-17 14:04 ` Will Deacon
3 siblings, 0 replies; 5+ messages in thread
From: Vincenzo Frascino @ 2022-05-17 13:16 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon
Cc: linux-arm-kernel, Steven Price, Vladimir Murzin
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>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>
> 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)
--
Regards,
Vincenzo
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE
2022-05-17 9:35 [PATCH v2] arm64: mte: Ensure the cleared tags are visible before setting the PTE Catalin Marinas
` (2 preceding siblings ...)
2022-05-17 13:16 ` Vincenzo Frascino
@ 2022-05-17 14:04 ` Will Deacon
3 siblings, 0 replies; 5+ messages in thread
From: Will Deacon @ 2022-05-17 14:04 UTC (permalink / raw)
To: Catalin Marinas
Cc: kernel-team, Will Deacon, Steven Price, Vladimir Murzin,
linux-arm-kernel, Vincenzo Frascino
On Tue, 17 May 2022 10:35:32 +0100, 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.
>
>
> [...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64: mte: Ensure the cleared tags are visible before setting the PTE
https://git.kernel.org/arm64/c/1d0cb4c8864a
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
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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
2022-05-17 10:23 ` Steven Price
2022-05-17 13:16 ` Vincenzo Frascino
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