cifs: Fix infinite loop when using hard mount option
commit 7ffbe65578b44fafdef577a360eb0583929f7c6e upstream.
For every request we send, whether it is SMB1 or SMB2+, we attempt to
reconnect tcon (cifs_reconnect_tcon or smb2_reconnect) before carrying
out the request.
So, while server->tcpStatus != CifsNeedReconnect, we wait for the
reconnection to succeed on wait_event_interruptible_timeout(). If it
returns, that means that either the condition was evaluated to true, or
timeout elapsed, or it was interrupted by a signal.
Since we're not handling the case where the process woke up due to a
received signal (-ERESTARTSYS), the next call to
wait_event_interruptible_timeout() will _always_ fail and we end up
looping forever inside either cifs_reconnect_tcon() or smb2_reconnect().
Here's an example of how to trigger that:
$ mount.cifs //foo/share /mnt/test -o
username=foo,password=foo,vers=1.0,hard
(break connection to server before executing bellow cmd)
$ stat -f /mnt/test & sleep 140
[1] 2511
$ ps -aux -q 2511
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 2511 0.0 0.0 12892 1008 pts/0 S 12:24 0:00 stat -f
/mnt/test
$ kill -9 2511
(wait for a while; process is stuck in the kernel)
$ ps -aux -q 2511
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 2511 83.2 0.0 12892 1008 pts/0 R 12:24 30:01 stat -f
/mnt/test
By using 'hard' mount point means that cifs.ko will keep retrying
indefinitely, however we must allow the process to be killed otherwise
it would hang the system.
Signed-off-by: Paulo Alcantara <palcantara@suse.de>
Cc: stable@vger.kernel.org
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2 files changed