From: Catalin Marinas <catalin.marinas@arm•com>
To: Steven Price <steven.price@arm•com>
Cc: Marc Zyngier <maz@kernel•org>, Will Deacon <will@kernel•org>,
James Morse <james.morse@arm•com>,
Julien Thierry <julien.thierry.kdev@gmail•com>,
Suzuki K Poulose <suzuki.poulose@arm•com>,
kvmarm@lists•cs.columbia.edu,
linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, Dave Martin <Dave.Martin@arm•com>,
Mark Rutland <mark.rutland@arm•com>,
Thomas Gleixner <tglx@linutronix•de>,
qemu-devel@nongnu•org, Juan Quintela <quintela@redhat•com>,
"Dr. David Alan Gilbert" <dgilbert@redhat•com>,
Richard Henderson <richard.henderson@linaro•org>,
Peter Maydell <peter.maydell@linaro•org>,
Haibo Xu <Haibo.Xu@arm•com>, Andrew Jones <drjones@redhat•com>
Subject: Re: [PATCH v12 1/8] arm64: mte: Handle race when synchronising tags
Date: Wed, 19 May 2021 18:32:28 +0100 [thread overview]
Message-ID: <20210519173228.GC21619@arm.com> (raw)
In-Reply-To: <20210517123239.8025-2-steven.price@arm.com>
On Mon, May 17, 2021 at 01:32:32PM +0100, Steven Price wrote:
> mte_sync_tags() used test_and_set_bit() to set the PG_mte_tagged flag
> before restoring/zeroing the MTE tags. However if another thread were to
> race and attempt to sync the tags on the same page before the first
> thread had completed restoring/zeroing then it would see the flag is
> already set and continue without waiting. This would potentially expose
> the previous contents of the tags to user space, and cause any updates
> that user space makes before the restoring/zeroing has completed to
> potentially be lost.
>
> Since this code is run from atomic contexts we can't just lock the page
> during the process. Instead implement a new (global) spinlock to protect
> the mte_sync_page_tags() function.
>
> Fixes: 34bfeea4a9e9 ("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE")
> Signed-off-by: Steven Price <steven.price@arm•com>
Other than the missing spinlock initialisation, the patch looks fine to
me.
Reviewed-by: Catalin Marinas <catalin.marinas@arm•com>
(though I'll probably queue it as a fix, waiting a couple of days for
comments)
--
Catalin
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next prev parent reply other threads:[~2021-05-19 17:34 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 12:32 [PATCH v12 0/8] MTE support for KVM guest Steven Price
2021-05-17 12:32 ` [PATCH v12 1/8] arm64: mte: Handle race when synchronising tags Steven Price
2021-05-17 14:03 ` Marc Zyngier
2021-05-17 14:56 ` Steven Price
2021-05-19 17:32 ` Catalin Marinas [this message]
2021-05-17 12:32 ` [PATCH v12 2/8] arm64: Handle MTE tags zeroing in __alloc_zeroed_user_highpage() Steven Price
2021-05-17 12:32 ` [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Steven Price
2021-05-17 16:14 ` Marc Zyngier
2021-05-19 9:32 ` Steven Price
2021-05-19 17:48 ` Catalin Marinas
2021-05-19 18:06 ` Catalin Marinas
2021-05-20 11:55 ` Steven Price
2021-05-20 12:25 ` Catalin Marinas
2021-05-20 13:02 ` Catalin Marinas
2021-05-20 13:03 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 4/8] arm64: kvm: Introduce MTE VM feature Steven Price
2021-05-17 16:45 ` Marc Zyngier
2021-05-19 10:48 ` Steven Price
2021-05-20 8:51 ` Marc Zyngier
2021-05-20 14:46 ` Steven Price
2021-05-20 11:54 ` Catalin Marinas
2021-05-20 15:05 ` Steven Price
2021-05-20 17:50 ` Catalin Marinas
2021-05-21 9:28 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 5/8] arm64: kvm: Save/restore MTE registers Steven Price
2021-05-17 17:17 ` Marc Zyngier
2021-05-19 13:04 ` Steven Price
2021-05-20 9:46 ` Marc Zyngier
2021-05-20 15:21 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 6/8] arm64: kvm: Expose KVM_ARM_CAP_MTE Steven Price
2021-05-17 17:40 ` Marc Zyngier
2021-05-19 13:26 ` Steven Price
2021-05-20 10:09 ` Marc Zyngier
2021-05-20 10:51 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 7/8] KVM: arm64: ioctl to fetch/store tags in a guest Steven Price
2021-05-17 18:04 ` Marc Zyngier
2021-05-19 13:51 ` Steven Price
2021-05-20 12:05 ` Catalin Marinas
2021-05-20 15:58 ` Steven Price
2021-05-20 17:27 ` Catalin Marinas
2021-05-21 9:42 ` Steven Price
2021-05-24 18:11 ` Catalin Marinas
2021-05-27 7:50 ` Steven Price
2021-05-27 13:08 ` Catalin Marinas
2021-05-17 12:32 ` [PATCH v12 8/8] KVM: arm64: Document MTE capability and ioctl Steven Price
2021-05-17 18:09 ` Marc Zyngier
2021-05-19 14:09 ` Steven Price
2021-05-20 10:24 ` Marc Zyngier
2021-05-20 10:52 ` Steven Price
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