linux-kernel - [PATCH 3.16 13/16] KVM: use after free in kvm_ioctl_create

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Date:   Fri, 22 Mar 2019 05:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Radim Krčmář" <rkrcmar@...hat.com>,
        "David Hildenbrand" <david@...hat.com>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: [PATCH 3.16 13/16] KVM: use after free in kvm_ioctl_create_device()

3.16.64-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@...cle.com>

commit a0f1d21c1ccb1da66629627a74059dd7f5ac9c61 upstream.

We should move the ops->destroy(dev) after the list_del(&dev->vm_node)
so that we don't use "dev" after freeing it.

Fixes: a28ebea2adc4 ("KVM: Protect device ops->create and list_add with kvm->lock")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 virt/kvm/kvm_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2342,10 +2342,10 @@ static int kvm_ioctl_create_device(struc
 
 	ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | O_CLOEXEC);
 	if (ret < 0) {
-		ops->destroy(dev);
 		mutex_lock(&kvm->lock);
 		list_del(&dev->vm_node);
 		mutex_unlock(&kvm->lock);
+		ops->destroy(dev);
 		return ret;
 	}