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

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vhost_net_ubuf_put_and_wait has a confusing name:
it will actually also free it's argument.
Thus since commit 1280c27f8e
    "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 <asias@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin 2013-07-07 14:26:53 +03:00 committed by David S. Miller
parent 785bf6f790
commit dd7633ecd5
1 changed files with 7 additions and 2 deletions
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9
drivers/vhost/net.c
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@ -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 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
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: