[PATCH 4.4 21/31] vhost_net: validate sock before trying to put its fd

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Jason Wang <jasowang@xxxxxxxxxx>

[ Upstream commit b8f1f65882f07913157c44673af7ec0b308d03eb ]

Sock will be NULL if we pass -1 to vhost_net_set_backend(), but when
we meet errors during ubuf allocation, the code does not check for
NULL before calling sockfd_put(), this will lead NULL
dereferencing. Fixing by checking sock pointer before.

Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support")
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/vhost/net.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -955,7 +955,8 @@ err_used:
 	if (ubufs)
 		vhost_net_ubuf_put_wait_and_free(ubufs);
 err_ubufs:
-	sockfd_put(sock);
+	if (sock)
+		sockfd_put(sock);
 err_vq:
 	mutex_unlock(&vq->mutex);
 err: