Commit 50bd7d5a authored Jul 05, 2022 by Shyam Prasad N Committed by Steve French Jul 12, 2022

cifs: fix race condition with delayed threads



On failure to create a new channel, first cancel the
delayed threads, which could try to search for this
channel, and not find it.

The other option was to put the tcp session for the
channel first, before decrementing chan_count. But
that would leave a reference to the tcp session, when
it has been freed already.

So going with the former option and cancelling the
delayed works first, before rolling back the channel.

Fixes: aa45dadd ("cifs: change iface_list from array to sorted linked list")
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

parent 32346491

fs/cifs/sess.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -474,6 +474,14 @@ cifs_ses_add_channel(struct cifs_sb_info cifs_sb, struct cifs_ses ses,

		out:
		if (rc && chan->server) {
		/*
		* we should avoid race with these delayed works before we
		* remove this channel
		*/
		cancel_delayed_work_sync(&chan->server->echo);
		cancel_delayed_work_sync(&chan->server->resolve);
		cancel_delayed_work_sync(&chan->server->reconnect);

		spin_lock(&ses->chan_lock);
		/* we rely on all bits beyond chan_count to be clear */
		cifs_chan_clear_need_reconnect(ses, chan->server);
		@@ -484,10 +492,9 @@ cifs_ses_add_channel(struct cifs_sb_info cifs_sb, struct cifs_ses ses,
		*/
		WARN_ON(ses->chan_count < 1);
		spin_unlock(&ses->chan_lock);
		}

		if (rc && chan->server)
		cifs_put_tcp_session(chan->server, 0);
		}

		return rc;
		}