From e1f0a18c9564cdb16523c802e2c6fe5874e3d944 Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Wed, 11 Mar 2026 15:06:02 +0800 Subject: [PATCH] net/rose: fix NULL pointer dereference in rose_transmit_link on reconnect syzkaller reported a bug [1], and the reproducer is available at [2]. ROSE sockets use four sk->sk_state values: TCP_CLOSE, TCP_LISTEN, TCP_SYN_SENT, and TCP_ESTABLISHED. rose_connect() already rejects calls for TCP_ESTABLISHED (-EISCONN) and TCP_CLOSE with SS_CONNECTING (-ECONNREFUSED), but lacks a check for TCP_SYN_SENT. When rose_connect() is called a second time while the first connection attempt is still in progress (TCP_SYN_SENT), it overwrites rose->neighbour via rose_get_neigh(). If that returns NULL, the socket is left with rose->state == ROSE_STATE_1 but rose->neighbour == NULL. When the socket is subsequently closed, rose_release() sees ROSE_STATE_1 and calls rose_write_internal() -> rose_transmit_link(skb, NULL), causing a NULL pointer dereference. Per connect(2), a second connect() while a connection is already in progress should return -EALREADY. Add this missing check for TCP_SYN_SENT to complete the state validation in rose_connect(). [1] https://syzkaller.appspot.com/bug?extid=d00f90e0af54102fb271 [2] https://gist.github.com/mrpre/9e6779e0d13e2c66779b1653fef80516 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+d00f90e0af54102fb271@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69694d6f.050a0220.58bed.0027.GAE@google.com/T/ Suggested-by: Eric Dumazet Signed-off-by: Jiayuan Chen Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260311070611.76913-1-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski --- net/rose/af_rose.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c index 841d62481048..ba56213e0a2a 100644 --- a/net/rose/af_rose.c +++ b/net/rose/af_rose.c @@ -811,6 +811,11 @@ static int rose_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int goto out_release; } + if (sk->sk_state == TCP_SYN_SENT) { + err = -EALREADY; + goto out_release; + } + sk->sk_state = TCP_CLOSE; sock->state = SS_UNCONNECTED;