smb3: missing lock when picking channel

smfrench · smfrench · commit 8094a600245e · 2024-04-25T12:47:23.000-05:00
Coverity spotted a place where we should have been holding the
channel lock when accessing the ses channel index.

Addresses-Coverity: 1582039 ("Data race condition (MISSING_LOCK)")
Cc: stable@vger.kernel.org
Reviewed-by: Shyam Prasad N &lt;sprasad@microsoft.com&gt;
Signed-off-by: Steve French &lt;stfrench@microsoft.com&gt;
diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
@@ -1057,9 +1057,11 @@ struct TCP_Server_Info *cifs_pick_channel(struct cifs_ses *ses)
 		index = (uint)atomic_inc_return(&ses->chan_seq);
 		index %= ses->chan_count;
 	}
+
+	server = ses->chans[index].server;
 	spin_unlock(&ses->chan_lock);
 
-	return ses->chans[index].server;
+	return server;
 }
 
 int

Original file line number	Diff line number	Diff line change
`@@ -1057,9 +1057,11 @@ struct TCP_Server_Info cifs_pick_channel(struct cifs_ses ses)`
`1057`	`1057`	`index = (uint)atomic_inc_return(&ses->chan_seq);`
`1058`	`1058`	`index %= ses->chan_count;`
`1059`	`1059`	`}`
	`1060`	`+`
	`1061`	`+ server = ses->chans[index].server;`
`1060`	`1062`	`spin_unlock(&ses->chan_lock);`
`1061`	`1063`
`1062`		`- return ses->chans[index].server;`
	`1064`	`+ return server;`
`1063`	`1065`	`}`
`1064`	`1066`
`1065`	`1067`	`int`