In the Linux kernel, the following vulnerability has been resolved:
smb: client: cancel reconnect work in clean_demultiplex_info()
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.
