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cifs: Fix infinite loop when using hard mount option

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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>
This commit is contained in:
Paulo Alcantara 2018-07-05 13:46:34 -03:00 committed by Steve French
parent f46ecbd97f
commit 7ffbe65578
2 changed files with 20 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
fs/cifs/cifssmb.c
View File

@ -157,8 +157,14 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
* greater than cifs socket timeout which is 7 seconds
*/
while (server->tcpStatus == CifsNeedReconnect) {
wait_event_interruptible_timeout(server->response_q,
(server->tcpStatus != CifsNeedReconnect), 10 * HZ);
rc = wait_event_interruptible_timeout(server->response_q,
(server->tcpStatus != CifsNeedReconnect),
10 * HZ);
if (rc < 0) {
cifs_dbg(FYI, "%s: aborting reconnect due to a received"
" signal by the process\n", __func__);
return -ERESTARTSYS;
}
/* are we still trying to reconnect? */
if (server->tcpStatus != CifsNeedReconnect)

18
fs/cifs/smb2pdu.c
View File

@ -155,7 +155,7 @@ out:
static int
smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
{
int rc = 0;
int rc;
struct nls_table *nls_codepage;
struct cifs_ses *ses;
struct TCP_Server_Info *server;
@ -166,10 +166,10 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
* for those three - in the calling routine.
*/
if (tcon == NULL)
return rc;
return 0;
if (smb2_command == SMB2_TREE_CONNECT)
return rc;
return 0;
if (tcon->tidStatus == CifsExiting) {
/*
@ -212,8 +212,14 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
return -EAGAIN;
}
wait_event_interruptible_timeout(server->response_q,
(server->tcpStatus != CifsNeedReconnect), 10 * HZ);
rc = wait_event_interruptible_timeout(server->response_q,
(server->tcpStatus != CifsNeedReconnect),
10 * HZ);
if (rc < 0) {
cifs_dbg(FYI, "%s: aborting reconnect due to a received"
" signal by the process\n", __func__);
return -ERESTARTSYS;
}
/* are we still trying to reconnect? */
if (server->tcpStatus != CifsNeedReconnect)
@ -231,7 +237,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
}
if (!tcon->ses->need_reconnect && !tcon->need_reconnect)
return rc;
return 0;
nls_codepage = load_nls_default();