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    Subject[PATCH 5.14 023/169] KVM: arm64: Release mmap_lock when using VM_SHARED with MTE
    Date
    From: Quentin Perret <qperret@google.com>

    [ Upstream commit 6e6a8ef088e1222cb1250942f51ad9c1ab219ab2 ]

    VM_SHARED mappings are currently forbidden in a memslot with MTE to
    prevent two VMs racing to sanitise the same page. However, this check
    is performed while holding current->mm's mmap_lock, but fails to release
    it. Fix this by releasing the lock when needed.

    Fixes: ea7fc1bb1cd1 ("KVM: arm64: Introduce MTE VM feature")
    Signed-off-by: Quentin Perret <qperret@google.com>
    Signed-off-by: Marc Zyngier <maz@kernel.org>
    Link: https://lore.kernel.org/r/20211005122031.809857-1-qperret@google.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm64/kvm/mmu.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
    index 0625bf2353c2..3fcdacfee579 100644
    --- a/arch/arm64/kvm/mmu.c
    +++ b/arch/arm64/kvm/mmu.c
    @@ -1477,8 +1477,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
    * when updating the PG_mte_tagged page flag, see
    * sanitise_mte_tags for more details.
    */
    - if (kvm_has_mte(kvm) && vma->vm_flags & VM_SHARED)
    - return -EINVAL;
    + if (kvm_has_mte(kvm) && vma->vm_flags & VM_SHARED) {
    + ret = -EINVAL;
    + break;
    + }

    if (vma->vm_flags & VM_PFNMAP) {
    /* IO region dirty page logging not allowed */
    --
    2.33.0


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