cifs: fix CIFS_IOC_GET_MNT_INFO oops

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

Fixes: 0de1f4c6f6c0 ("Add way to query server fs info for smb3")
Cc: stable@vger.kernel.org
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 4d598a71cf84..76fb0917dc8c 100644
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -209,6 +209,8 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
                                 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;