[PATCH 4.4 40/56] cifs: fix CIFS_IOC_GET_MNT_INFO oops

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Disseldorp <dd...@suse.de>

commit d8a6e505d6bba2250852fbc1c1c86fe68aaf9af3 upstream.

An open directory may have a NULL private_data pointer prior to readdir.

Fixes: 0de1f4c6f6c0 ("Add way to query server fs info for smb3")
Signed-off-by: David Disseldorp <dd...@suse.de>
Signed-off-by: Steve French <smfre...@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/cifs/ioctl.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -272,6 +272,8 @@ long cifs_ioctl(struct file *filep, unsi
                                rc = -EOPNOTSUPP;
                        break;
                case CIFS_IOC_GET_MNT_INFO:
+                       if (pSMBFile == NULL)
+                               break;
                        tcon = tlink_tcon(pSMBFile->tlink);
                        rc = smb_mnt_get_fsinfo(xid, tcon, (void __user *)arg);
                        break;