On Fri, Feb 21, 2020 at 12:06:56PM +0100, Eugenio Pérez wrote:

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

Thanks for debugging this!

Acked-by: Michael S. Tsirkin mst@redhat.com

---

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

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index e158159671fa..18e205eeb9af 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -1414,10 +1414,6 @@ 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);

@@ -1430,11 +1426,7 @@ 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; }

-- 2.18.1