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

PATCH Superseded Michael S. Tsirkin 1 participant 1 message Jun 20, 2013

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Networking Network drivers KVM virtio core +1 more subsystems

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Michael S. Tsirkin

author maintainer

2013-06-20 11:50 UTC #0 lore raw

PATCH 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 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.

Signed-off-by Michael S. Tsirkin <[email protected]>

---

I sent the same patch against 3.10 separately.
This one is for stable, against 3.9/3.8 - the code moved around since then.
Not sending to stable directly since Dave Miller handles it for net drivers normally.

 drivers/vhost/net.c   | 4 ++--
 drivers/vhost/vhost.c | 5 +++++
 drivers/vhost/vhost.h | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

drivers/vhost/net.c +2 -2

index ec6fb3f..e5ff7a5 100644
@@ -856,7 +856,7 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 	mutex_unlock(&vq->mutex);
 
 	if (oldubufs) {
-		vhost_ubuf_put_and_wait(oldubufs);
+		vhost_ubuf_put_wait_and_free(oldubufs);
 		mutex_lock(&vq->mutex);
 		vhost_zerocopy_signal_used(n, vq);
 		mutex_unlock(&vq->mutex);

@@ -874,7 +874,7 @@ err_used:
 	rcu_assign_pointer(vq->private_data, oldsock);
 	vhost_net_enable_vq(n, vq);
 	if (ubufs)
-		vhost_ubuf_put_and_wait(ubufs);
+		vhost_ubuf_put_wait_and_free(ubufs);
 err_ubufs:
 	fput(sock->file);
 err_vq:

drivers/vhost/vhost.c +5 -0

index 9759249..c01d22f 100644
@@ -1581,5 +1581,10 @@ void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
 {
 	kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
 	wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
+}
+
+void vhost_ubuf_put_wait_and_free(struct vhost_ubuf_ref *ubufs)
+{
+	vhost_ubuf_put_and_wait(ubufs);
 	kfree(ubufs);
 }

drivers/vhost/vhost.h +1 -0

index 17261e2..b53cb28 100644
@@ -63,6 +63,7 @@ struct vhost_ubuf_ref {
 struct vhost_ubuf_ref *vhost_ubuf_alloc(struct vhost_virtqueue *, bool zcopy);
 void vhost_ubuf_put(struct vhost_ubuf_ref *);
 void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *);
+void vhost_ubuf_put_wait_and_free(struct vhost_ubuf_ref *);
 
 struct ubuf_info;

Signature · 1 line

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