From 5b0c911bcdbd982f7748d11c0b39ec5808eae2de Mon Sep 17 00:00:00 2001 From: Morduan Zang Date: Thu, 23 Apr 2026 09:05:57 +0800 Subject: [PATCH] net: phonet: do not BUG_ON() in pn_socket_autobind() on failed bind MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Suggested-by: Remi Denis-Courmont Signed-off-by: Morduan Zang Signed-off-by: zhanjun Acked-by: Rémi Denis-Courmont Link: https://patch.msgid.link/87A8960A2045AF3C+20260423010557.138124-1-zhangdandan@uniontech.com Signed-off-by: Jakub Kicinski --- net/phonet/socket.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/net/phonet/socket.c b/net/phonet/socket.c index c4af26357144..631a99cdbd00 100644 --- a/net/phonet/socket.c +++ b/net/phonet/socket.c @@ -208,9 +208,15 @@ static int pn_socket_autobind(struct socket *sock) sa.spn_family = AF_PHONET; err = pn_socket_bind(sock, (struct sockaddr_unsized *)&sa, sizeof(struct sockaddr_pn)); - if (err != -EINVAL) + /* + * pn_socket_bind() also returns -EINVAL when sk_state != TCP_CLOSE + * without a prior bind, so -EINVAL alone is not sufficient to infer + * that the socket was already bound. Only treat it as "already + * bound" when the port is non-zero; otherwise propagate the error + * instead of crashing the kernel. + */ + if (err != -EINVAL || unlikely(!pn_port(pn_sk(sock->sk)->sobject))) return err; - BUG_ON(!pn_port(pn_sk(sock->sk)->sobject)); return 0; /* socket was already bound */ }