CVE-2026-23460: net/rose: fix NULL pointer dereference in rose_transmit_link on reconnect

In the Linux kernel, the following vulnerability has been resolved:

net/rose: fix NULL pointer dereference in rosetransmitlink on reconnect

syzkaller reported a bug [1], and the reproducer is available at [2].

ROSE sockets use four sk->skstate values: TCPCLOSE, TCPLISTEN, TCPSYNSENT, and TCPESTABLISHED. roseconnect() already rejects calls for TCPESTABLISHED (-EISCONN) and TCPCLOSE with SSCONNECTING (-ECONNREFUSED), but lacks a check for TCPSYNSENT.

When roseconnect() is called a second time while the first connection attempt is still in progress (TCPSYNSENT), it overwrites rose->neighbour via rosegetneigh(). If that returns NULL, the socket is left with rose->state == ROSESTATE1 but rose->neighbour == NULL. When the socket is subsequently closed, roserelease() sees ROSESTATE1 and calls rosewriteinternal() -> rosetransmitlink(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 TCPSYNSENT to complete the state validation in roseconnect().

[1] https://syzkaller.appspot.com/bug?extid=d00f90e0af54102fb271 [2] https://gist.github.com/mrpre/9e6779e0d13e2c66779b1653fef80516