smb3: fix unmount hang in open_shroot

An earlier patch "CIFS: fix deadlock in cached root handling"
did not completely address the deadlock in open_shroot. This
patch addresses the deadlock.

In testing the recent patch:
  smb3: improve handling of share deleted (and share recreated)
we were able to reproduce the open_shroot deadlock to one
of the target servers in unmount in a delete share scenario.

Fixes: 7e5a70ad88b1e ("CIFS: fix deadlock in cached root handling")

This is version 2 of this patch. An earlier version of this
patch "smb3: fix unmount hang in open_shroot" had a problem
found by Dan.

Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Suggested-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Aurelien Aptel <aaptel@suse.com>
CC: Stable <stable@vger.kernel.org>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 3672ce0..5776d7b 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -658,6 +658,15 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
                return 0;
        }
 
+       /*
+        * We do not hold the lock for the open because in case
+        * SMB2_open needs to reconnect, it will end up calling
+        * cifs_mark_open_files_invalid() which takes the lock again
+        * thus causing a deadlock
+        */
+
+       mutex_unlock(&tcon->crfid.fid_mutex);
+
        if (smb3_encryption_required(tcon))
                flags |= CIFS_TRANSFORM_REQ;
 
@@ -679,7 +688,7 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
 
        rc = SMB2_open_init(tcon, &rqst[0], &oplock, &oparms, &utf16_path);
        if (rc)
-               goto oshr_exit;
+               goto oshr_free;
        smb2_set_next_command(tcon, &rqst[0]);
 
        memset(&qi_iov, 0, sizeof(qi_iov));
@@ -692,18 +701,10 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
                                  sizeof(struct smb2_file_all_info) +
                                  PATH_MAX * 2, 0, NULL);
        if (rc)
-               goto oshr_exit;
+               goto oshr_free;
 
        smb2_set_related(&rqst[1]);
 
-       /*
-        * We do not hold the lock for the open because in case
-        * SMB2_open needs to reconnect, it will end up calling
-        * cifs_mark_open_files_invalid() which takes the lock again
-        * thus causing a deadlock
-        */
-
-       mutex_unlock(&tcon->crfid.fid_mutex);
        rc = compound_send_recv(xid, ses, flags, 2, rqst,
                                resp_buftype, rsp_iov);
        mutex_lock(&tcon->crfid.fid_mutex);