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vhost-net: fix use-after-free in vhost_net_flush

PATCH In review Michael S. Tsirkin 2 participants 2 messages Jul 7, 2013 – Jul 9, 2013

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Michael S. Tsirkin

author maintainer
#0 lore raw

PATCH v3 1/1 vhost-net: fix use-after-free in vhost_net_flush

vhost_net_ubuf_put_and_wait has a confusing name:
it will actually also free it's argument.
Thus since commit 1280c27f8e29acf4af2da914e80ec27c3dbd5c01
"vhost-net: flush outstanding DMAs on memory change"
vhost_net_flush tries to use the argument after passing it to vhost_net_ubuf_put_and_wait, this results
in use after free.
To fix, don't free the argument in vhost_net_ubuf_put_and_wait, add an new API for callers that want to free ubufs.

Acked-by Asias He <[email protected]>
Acked-by Jason Wang <[email protected]>
Signed-off-by Michael S. Tsirkin <[email protected]>

---

Please review, and queue for 3.11 and stable.

Changes from v2:
- rebased to net/master
Changes from v1:
- tweak commit message

 drivers/vhost/net.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
drivers/vhost/net.c +7 -2
index f80d3dd..8ca5ac7 100644
@@ -150,6 +150,11 @@ static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs)
 {
 	kref_put(&ubufs->kref, vhost_net_zerocopy_done_signal);
 	wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
+}
+
+static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs)
+{
+	vhost_net_ubuf_put_and_wait(ubufs);
 	kfree(ubufs);
 }
 

@@ -948,7 +953,7 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 	mutex_unlock(&vq->mutex);
 
 	if (oldubufs) {
-		vhost_net_ubuf_put_and_wait(oldubufs);
+		vhost_net_ubuf_put_wait_and_free(oldubufs);
 		mutex_lock(&vq->mutex);
 		vhost_zerocopy_signal_used(n, vq);
 		mutex_unlock(&vq->mutex);

@@ -966,7 +971,7 @@ err_used:
 	rcu_assign_pointer(vq->private_data, oldsock);
 	vhost_net_enable_vq(n, vq);
 	if (ubufs)
-		vhost_net_ubuf_put_and_wait(ubufs);
+		vhost_net_ubuf_put_wait_and_free(ubufs);
 err_ubufs:
 	fput(sock->file);
 err_vq:
Signature · 1 line
MST
maintainer
#1 lore raw

From: "Michael S. Tsirkin" <[email protected]>
Date: Sun, 7 Jul 2013 14:26:53 +0300

Quoted 10 lines

vhost_net_ubuf_put_and_wait has a confusing name:
it will actually also free it's argument.
Thus since commit 1280c27f8e29acf4af2da914e80ec27c3dbd5c01
"vhost-net: flush outstanding DMAs on memory change"
vhost_net_flush tries to use the argument after passing it to vhost_net_ubuf_put_and_wait, this results
in use after free.
To fix, don't free the argument in vhost_net_ubuf_put_and_wait, add an new API for callers that want to free ubufs.

Quoted 3 lines
Acked-by Asias He <[email protected]>
Acked-by Jason Wang <[email protected]>
Signed-off-by Michael S. Tsirkin <[email protected]>

Applied and queued up for -stable.