cifs: fix CIFS_ENUMERATE_SNAPSHOTS oops

commit 6026685de33b0db5b2b6b0e9b41b3a1a3261033c upstream.

As with 618763958b22, an open directory may have a NULL private_data
pointer prior to readdir. CIFS_ENUMERATE_SNAPSHOTS must check for this
before dereference.

Fixes: 834170c85978 ("Enable previous version support")
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 001528781b6b..b52b7ffa6d34 100644
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -268,6 +268,8 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
                         rc = smb_mnt_get_fsinfo(xid, tcon, (void __user *)arg);
                         break;
                 case CIFS_ENUMERATE_SNAPSHOTS:
+                        if (pSMBFile == NULL)
+                                break;
                         if (arg == 0) {
                                 rc = -EINVAL;
                                 goto cifs_ioc_exit;