From: Shyam Prasad N <sprasad@microsoft.com>
Date: Tue, 5 Jul 2022 11:16:24 +0000
Subject: [PATCH] cifs: fix race condition with delayed threads
Git-commit: 50bd7d5a647bdf533575111c5335f49707c2ce2f
References: bsc#1193629
Patch-mainline: v5.19-rc7

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: aa45dadd34e4 ("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>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/sess.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index b85718f32b53..02c8b2906196 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -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;
 }
-- 
2.37.3