From: Cornelia Huck <cohuck@redhat.com>
To: Peter Collingbourne <pcc@google.com>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Evgenii Stepanov <eugenis@google.com>,
kvm@vger.kernel.org, Steven Price <steven.price@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Peter Collingbourne <pcc@google.com>
Subject: Re: [PATCH v3 1/7] arm64: mte: Fix/clarify the PG_mte_tagged semantics
Date: Fri, 02 Sep 2022 12:26:25 +0200 [thread overview]
Message-ID: <87k06mdqcu.fsf@redhat.com> (raw)
In-Reply-To: <20220810193033.1090251-2-pcc@google.com>
On Wed, Aug 10 2022, Peter Collingbourne <pcc@google.com> wrote:
> From: Catalin Marinas <catalin.marinas@arm.com>
>
> Currently the PG_mte_tagged page flag mostly means the page contains
> valid tags and it should be set after the tags have been cleared or
> restored. However, in mte_sync_tags() it is set before setting the tags
> to avoid, in theory, a race with concurrent mprotect(PROT_MTE) for
> shared pages. However, a concurrent mprotect(PROT_MTE) with a copy on
> write in another thread can cause the new page to have stale tags.
> Similarly, tag reading via ptrace() can read stale tags of the
s/of/if/
> PG_mte_tagged flag is set before actually clearing/restoring the tags.
>
> Fix the PG_mte_tagged semantics so that it is only set after the tags
> have been cleared or restored. This is safe for swap restoring into a
> MAP_SHARED or CoW page since the core code takes the page lock. Add two
> functions to test and set the PG_mte_tagged flag with acquire and
> release semantics. The downside is that concurrent mprotect(PROT_MTE) on
> a MAP_SHARED page may cause tag loss. This is already the case for KVM
> guests if a VMM changes the page protection while the guest triggers a
> user_mem_abort().
>
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Peter Collingbourne <pcc@google.com>
> ---
> v3:
> - fix build with CONFIG_ARM64_MTE disabled
>
> arch/arm64/include/asm/mte.h | 30 ++++++++++++++++++++++++++++++
> arch/arm64/include/asm/pgtable.h | 2 +-
> arch/arm64/kernel/cpufeature.c | 4 +++-
> arch/arm64/kernel/elfcore.c | 2 +-
> arch/arm64/kernel/hibernate.c | 2 +-
> arch/arm64/kernel/mte.c | 12 +++++++-----
> arch/arm64/kvm/guest.c | 4 ++--
> arch/arm64/kvm/mmu.c | 4 ++--
> arch/arm64/mm/copypage.c | 4 ++--
> arch/arm64/mm/fault.c | 2 +-
> arch/arm64/mm/mteswap.c | 2 +-
> 11 files changed, 51 insertions(+), 17 deletions(-)
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
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next prev parent reply other threads:[~2022-09-02 10:29 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-10 19:30 [PATCH v3 0/7] KVM: arm64: permit MAP_SHARED mappings with MTE enabled Peter Collingbourne
2022-08-10 19:30 ` [PATCH v3 1/7] arm64: mte: Fix/clarify the PG_mte_tagged semantics Peter Collingbourne
2022-09-01 15:49 ` Catalin Marinas
2022-09-02 10:26 ` Cornelia Huck [this message]
2022-09-02 14:47 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 2/7] KVM: arm64: Simplify the sanitise_mte_tags() logic Peter Collingbourne
2022-09-02 14:47 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 3/7] mm: Add PG_arch_3 page flag Peter Collingbourne
2022-08-11 7:16 ` kernel test robot
2022-09-01 17:59 ` Catalin Marinas
2022-09-05 17:01 ` Catalin Marinas
2022-09-19 18:12 ` Marc Zyngier
2022-09-20 15:39 ` Catalin Marinas
2022-09-20 16:33 ` Marc Zyngier
2022-09-20 16:58 ` Catalin Marinas
2022-09-21 3:53 ` Peter Collingbourne
2022-08-10 19:30 ` [PATCH v3 4/7] arm64: mte: Lock a page for MTE tag initialisation Peter Collingbourne
2022-09-02 14:47 ` Steven Price
2022-09-02 16:28 ` Catalin Marinas
2022-09-02 16:58 ` Catalin Marinas
2022-09-05 7:37 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 5/7] KVM: arm64: unify the tests for VMAs in memslots when MTE is enabled Peter Collingbourne
2022-09-02 13:41 ` Catalin Marinas
2022-09-02 14:47 ` Steven Price
2022-08-10 19:30 ` [PATCH v3 6/7] KVM: arm64: permit all VM_MTE_ALLOWED mappings with MTE enabled Peter Collingbourne
2022-09-02 13:45 ` Catalin Marinas
2022-09-02 14:47 ` Steven Price
2022-09-12 16:23 ` Marc Zyngier
2022-09-13 4:10 ` Peter Collingbourne
2022-08-10 19:30 ` [PATCH v3 7/7] Documentation: document the ABI changes for KVM_CAP_ARM_MTE Peter Collingbourne
2022-09-02 13:49 ` Catalin Marinas
2022-09-02 14:05 ` [PATCH v3 0/7] KVM: arm64: permit MAP_SHARED mappings with MTE enabled Catalin Marinas
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