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smb3: fix unmount hang in open_shroot

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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: 7e5a70ad88 ("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>
This commit is contained in:
Steve French 2019-09-12 17:52:54 -05:00
parent 3e7a02d478
commit 96d9f7ed00
1 changed files with 11 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
fs/cifs/smb2ops.c
View File

@ -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);