clean_demultiplex_info() cancels server->echo delayed work but not server->reconnect, which can cause a use-after-free when the demultiplex thread exits while a reconnect work is still queued: cifs_demultiplex_thread() cifs_readv_from_socket() cifs_reconnect() __cifs_reconnect() cifs_queue_server_reconn() mod_delayed_work(cifsiod_wq, &server->reconnect, 0) clean_demultiplex_info() cancel_delayed_work_sync(&server->echo) // echo canceled // reconnect NOT canceled kfree_sensitive(server) // server freed ...later, on cifsiod_wq: smb2_reconnect_server() server->srv_count // UAF read of freed server Fix this by canceling server->reconnect delayed work in clean_demultiplex_info() before the server is freed, the same way cifs_put_tcp_session() already does. Reported-by: syzbot+5003556314abc915a71f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/6aa4a12d.f81106d8.2ab401.0023.GAE@google.com Fixes: 53e0e11efe92 ("CIFS: Fix a possible memory corruption during reconnect") Signed-off-by: Paulo Alcantara Cc: David Howells Cc: Shyam Prasad N Cc: Ronnie Sahlberg Cc: Tom Talpey Cc: Bharath SM Cc: Namjae Jeon Cc: stable@vger.kernel.org --- fs/smb/client/connect.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index b6e98eb31673..bef710d9a3c3 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -1067,6 +1067,7 @@ clean_demultiplex_info(struct TCP_Server_Info *server) spin_unlock(&server->srv_lock); cancel_delayed_work_sync(&server->echo); + cancel_delayed_work_sync(&server->reconnect); spin_lock(&server->srv_lock); server->tcpStatus = CifsExiting; -- 2.55.0