Patch "arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
arm-arm64-kvm-take-mmap_sem-in-kvm_arch_prepare_memory_region.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Marc Zyngier <[email protected]>
Date: Thu, 16 Mar 2017 18:20:50 +0000
Subject: arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region

From: Marc Zyngier <[email protected]>

commit 72f310481a08db821b614e7b5d00febcc9064b36 upstream.

We don't hold the mmap_sem while searching for VMAs (via find_vma), in kvm_arch_prepare_memory_region, which can end up in expected failures.

---
 arch/arm/kvm/mmu.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

@@ -1806,6 +1806,7 @@ int kvm_arch_prepare_memory_region(struc
 	    (KVM_PHYS_SIZE >> PAGE_SHIFT))
 		return -EFAULT;
 
+	down_read(&current->mm->mmap_sem);
 	/*
 	 * A memory region could potentially cover multiple VMAs, and any holes
 	 * between them, so iterate over all of them to find out if we can map

@@ -1849,8 +1850,10 @@ int kvm_arch_prepare_memory_region(struc
 			pa += vm_start - vma->vm_start;
 
 			/* IO region dirty page logging not allowed */
-			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
-				return -EINVAL;
+			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+				ret = -EINVAL;
+				goto out;
+			}
 
 			ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
 						    vm_end - vm_start,

@@ -1862,7 +1865,7 @@ int kvm_arch_prepare_memory_region(struc
 	} while (hva < reg_end);
 
 	if (change == KVM_MR_FLAGS_ONLY)
-		return ret;
+		goto out;
 
 	spin_lock(&kvm->mmu_lock);
 	if (ret)

@@ -1870,6 +1873,8 @@ int kvm_arch_prepare_memory_region(struc
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+out:
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kvm-arm-arm64-fix-locking-for-kvm_free_stage2_pgd.patch queue-4.9/arm-arm64-kvm-take-mmap_sem-in-kvm_arch_prepare_memory_region.patch queue-4.9/arm-arm64-kvm-take-mmap_sem-in-stage2_unmap_vm.patch