cifs: check for private_data before trying to put it

cifs_close doesn't check that the filp->private_data is non-NULL before
trying to put it. That can cause an oops in certain error conditions
that can occur on open or lookup before the private_data is set.

Reported-by: Ben Greear <greearb@candelatech.com>
CC: Stable <stable@kernel.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index c27d236738fc..5ae061c4ca25 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -575,8 +575,10 @@ reopen_error_exit:
 
 int cifs_close(struct inode *inode, struct file *file)
 {
-        cifsFileInfo_put(file->private_data);
-        file->private_data = NULL;
+        if (file->private_data != NULL) {
+                cifsFileInfo_put(file->private_data);
+                file->private_data = NULL;
+        }
 
         /* return code from the ->release op is always ignored */
         return 0;