From 78325fcb17f363748ba2a969b0d524be770427c8 Mon Sep 17 00:00:00 2001

From: Quentin Perret <qperret@google.com>

Date: Tue, 5 Oct 2021 13:20:31 +0100

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

Git-commit: 6e6a8ef088e1222cb1250942f51ad9c1ab219ab2

Patch-mainline: v5.15-rc7

References: stable-5.14.15

[ 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>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 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 */

-- 

2.26.2