nlm: Ensure callback code also checks that the files match

commit 251af29c upstream.

It is not sufficient to just check that the lock pids match when
granting a callback, we also need to ensure that we're granting
the callback on the right file.
Reported-by: Pankaj Singh <psingh.ait@gmail.com>
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
[bwh: Backported to 3.2: open-code file_inode()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

include/linux/lockd/lockd.h

@@ -348,7 +348,8 @@ static inline int nlm_privileged_requester(const struct svc_rqst *rqstp)
 static inline int nlm_compare_locks(const struct file_lock *fl1,
 				    const struct file_lock *fl2)
 {
-	return	fl1->fl_pid   == fl2->fl_pid
+	return fl1->fl_file->f_dentry->d_inode == fl2->fl_file->f_dentry->d_inode
+	     && fl1->fl_pid   == fl2->fl_pid
 	     && fl1->fl_owner == fl2->fl_owner
 	     && fl1->fl_start == fl2->fl_start
 	     && fl1->fl_end   == fl2->fl_end