cifs: check for private_data before trying to put it

commit 7797069305d13252fd66cf722aa8f2cbeb3c95cd upstream.

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>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e964b1cd5dd092bda83d274da53248a50dfd0ba3..7b2e8ec2709b308444a59a3ed0c0fd9fb9fe6d60 100644 (file)
--- 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;