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

Morduan Zang
2026-04-22T01:39:39Z

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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
Signed-off-by: Morduan Zang <zhangdandan@uniontech.com>
Signed-off-by: zhanjun <zhanjun@uniontech.com>
---
net/phonet/socket.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/phonet/socket.c b/net/phonet/socket.c
index 4423d483c630..de9108adfe1c 100644
--- a/net/phonet/socket.c
+++ b/net/phonet/socket.c
@@ -210,7 +210,15 @@ static int pn_socket_autobind(struct socket *sock)
sizeof(struct sockaddr_pn));
if (err != -EINVAL)
return err;
- BUG_ON(!pn_port(pn_sk(sock->sk)->sobject));
+ /*
+ * pn_socket_bind() can return -EINVAL both when the socket is
+ * already bound (pn_port() != 0) and when sk_state != TCP_CLOSE
+ * without a prior bind. Only the former is an "already bound"
+ * success for autobind; otherwise propagate -EINVAL instead of
+ * crashing the kernel.
+ */
+ if (!pn_port(pn_sk(sock->sk)->sobject))
+ return -EINVAL;
return 0; /* socket was already bound */
}

--
2.50.1