[PATCH 5.5 104/176] vhost: Check docket sk_family instead of call getname

Greg Kroah-Hartman
2020-03-03T17:50:04Z

From: Eugenio Pérez <eperezma@redhat.com>

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>

---
drivers/vhost/net.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1414,10 +1414,6 @@ static int vhost_net_release(struct inod

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);

@@ -1430,11 +1426,7 @@ static struct socket *get_raw_socket(int
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;
}