2021-10-05 12:24:11

by Quentin Perret

Subject: [PATCH] KVM: arm64: Release mmap_lock when using VM_SHARED with MTE

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 <[email protected]>
---
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 1a94a7ca48f2..69bd1732a299 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1529,8 +1529,10 @@ 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 */
--
2.33.0.800.g4c38ced690-goog

2021-10-05 12:27:45

by Marc Zyngier

Subject: Re: [PATCH] KVM: arm64: Release mmap_lock when using VM_SHARED with MTE

On Tue, 5 Oct 2021 13:20:31 +0100, Quentin Perret wrote:
> 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.

Applied to fixes, thanks!

[1/1] KVM: arm64: Release mmap_lock when using VM_SHARED with MTE
commit: 6e6a8ef088e1222cb1250942f51ad9c1ab219ab2

Cheers,

M.
--
Without deviation from the norm, progress is not possible.