Re: [PATCH net v2] net: phonet: do not BUG_ON() in pn_socket_autobind() on failed bind

[Rémi Denis-Courmont]

Le 23 avril 2026 04:05:57 GMT+03:00, Morduan Zang <zhangdandan@xxxxxxxxxxxxx> a écrit :
>syzbot reported a kernel BUG triggered from pn_socket_sendmsg() via
>pn_socket_autobind():
>
>  kernel BUG at net/phonet/socket.c:213!
>  RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
>  RIP: 0010:pn_socket_sendmsg+0x240/0x250 net/phonet/socket.c:421
>  Call Trace:
>   sock_sendmsg_nosec+0x112/0x150 net/socket.c:797
>   __sock_sendmsg net/socket.c:812 [inline]
>   __sys_sendto+0x402/0x590 net/socket.c:2280
>   ...
>
>pn_socket_autobind() calls pn_socket_bind() with port 0 and, on
>-EINVAL, assumes the socket was already bound and asserts that the
>port is non-zero:
>
>  err = pn_socket_bind(sock, ..., sizeof(struct sockaddr_pn));
>  if (err != -EINVAL)
>          return err;
>  BUG_ON(!pn_port(pn_sk(sock->sk)->sobject));
>  return 0; /* socket was already bound */
>
>However pn_socket_bind() also returns -EINVAL when sk->sk_state is not
>TCP_CLOSE, even when the socket has never been bound and pn_port() is
>still 0.  In that case the BUG_ON() fires and panics the kernel from a
>user-triggerable path.
>
>Treat the "bind returned -EINVAL but pn_port() is still 0" case as a
>regular error and propagate -EINVAL to the caller instead of crashing.
>Existing callers already translate a non-zero return from
>pn_socket_autobind() into -ENOBUFS/-EAGAIN, so returning -EINVAL here
>only changes behaviour from panic to a normal errno.
>
>Fixes: ba113a94b750 ("Phonet: common socket glue")
>Reported-by: syzbot+706f5eb79044e686c794@xxxxxxxxxxxxxxxxxxxxxxxxx
>Closes: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
>Suggested-by: Remi Denis-Courmont <courmisch@xxxxxxxxx>
>Signed-off-by: Morduan Zang <zhangdandan@xxxxxxxxxxxxx>
>Signed-off-by: zhanjun <zhanjun@xxxxxxxxxxxxx>

Acked-by: Rémi Denis-Courmont <remi@xxxxxxxxxx>