In the Linux kernel, the following vulnerability has been resolved: ksmbd: remove stale channels…

Why it is Amber

• CVSS 8.8 high
• On your watchlist: linux kernel

References

• https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f
• https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955
• https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5
• https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36
• https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d

Original description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: remove stale channels from all sessions on teardown ksmbd_sessions_deregister() removes a connection's channels from other sessions' channel lists only while conn->binding is still set: if (conn->binding) { hash_for_each_safe(sessions_table, ...) ksmbd_chann_del(conn, sess); } conn->binding is a transient flag: it is cleared once a binding SESSION_SETUP completes, and also by a subsequent non-binding SESSION_SETUP on the same connection (a reauthentication on a bound channel, or a new SessionId==0 setup). A connection that has bound a channel into another session's ksmbd_chann_list and then clears conn->binding leaves that channel behind when it disconnects: the channel, whose chann->conn points at the now freed struct ksmbd_conn, stays on the owner session's list. When the owning connection later tears down, the second loop dereferences the stale channel: xa_for_each(&sess->ksmbd_chann_list, chann_id, chann) if (chann->conn != conn) ksmbd_conn_set_exiting(chann->conn); /* freed */ which is a use-after-free write into the freed ksmbd_conn (the same stale channel is also walked by show_proc_session() through /proc). The session is leaked as well, because its channel list never empties. Remove the conn->binding gate so a connection always removes its channels from every session on teardown.