CVE-2026-23460

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

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