vhost: Check docket sk_family instead of call getname

commit 42d84c8490f9f0931786f1623191fcab397c3d64 upstream.

Doing so, we save one call to get data we already have in the struct.

Also, since there is no guarantee that getname use sockaddr_ll
parameter beyond its size, we add a little bit of security here.
It should do not do beyond MAX_ADDR_LEN, but syzbot found that
ax25_getname writes more (72 bytes, the size of full_sockaddr_ax25,
versus 20 + 32 bytes of sockaddr_ll + MAX_ADDR_LEN in syzbot repro).

Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server")
Reported-by: syzbot+f2a62d07a5198c819c7b@syzkaller.appspotmail.com
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 124356d..88c8c15 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1187,10 +1187,6 @@ static int vhost_net_release(struct inode *inode, struct file *f)
 
 static struct socket *get_raw_socket(int fd)
 {
-       struct {
-               struct sockaddr_ll sa;
-               char  buf[MAX_ADDR_LEN];
-       } uaddr;
        int r;
        struct socket *sock = sockfd_lookup(fd, &r);
 
@@ -1203,11 +1199,7 @@ static struct socket *get_raw_socket(int fd)
                goto err;
        }
 
-       r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa, 0);
-       if (r < 0)
-               goto err;
-
-       if (uaddr.sa.sll_family != AF_PACKET) {
+       if (sock->sk->sk_family != AF_PACKET) {
                r = -EPFNOSUPPORT;
                goto err;
        }