[PATCH 4.9 63/80] cifs: fix CIFS_IOC_GET_MNT_INFO oops

[Greg Kroah-Hartman]

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

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

From: David Disseldorp <ddiss@xxxxxxx>

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 <ddiss@xxxxxxx>
Signed-off-by: Steve French <smfrench@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -264,6 +264,8 @@ 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;