From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754199Ab2GWPUm (ORCPT ); Mon, 23 Jul 2012 11:20:42 -0400 Received: from fieldses.org ([174.143.236.118]:48561 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754166Ab2GWPUk (ORCPT ); Mon, 23 Jul 2012 11:20:40 -0400 Date: Mon, 23 Jul 2012 11:20:39 -0400 To: Linus Torvalds Cc: Dave Jones , Linux Kernel , "J. Bruce Fields" Subject: Re: Remove easily user-triggerable BUG from generic_setlease Message-ID: <20120723152038.GB623@fieldses.org> References: <20120713173536.GB25432@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) From: "J. Bruce Fields" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 13, 2012 at 10:47:43AM -0700, Linus Torvalds wrote: > On Fri, Jul 13, 2012 at 10:35 AM, Dave Jones wrote: > > This can be trivially triggered from userspace by passing in something unexpected. > > Argh. It looks like it would be harmless (apart from the noise), > except we hold file_lock_lock. Which turns the BUG_ON() into not just > "noise and kill the process", but "noise and kill the process and > leave a nasty lock held". > > This seems to go back to 3.2, so stable should be cc'd, no? Thanks! Yes, this fixes the bug for >=3.2, but before the addition of this BUG() we could get memory corruption in this case. And that problem existed since the original introduction of the lease code, as far as I can tell. So we need something like the following, backported to 2.6.anything. --b. commit 76fca57d7f4e408fc758a42f798c2ebef54be60f Author: J. Bruce Fields Date: Wed Jul 18 17:45:42 2012 -0600 locks: fix checking of fcntl_setlease argument The only checks of the long argument passed to fcntl(fd,F_SETLEASE,.) are done after converting the long to an int. Thus some illegal values may be let through and cause problems in later code. Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields diff --git a/fs/locks.c b/fs/locks.c index 43797a9..ad1de47 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -311,7 +311,7 @@ static int flock_make_lock(struct file *filp, struct file_lock **lock, return 0; } -static int assign_type(struct file_lock *fl, int type) +static int assign_type(struct file_lock *fl, long type) { switch (type) { case F_RDLCK: @@ -448,7 +448,7 @@ static const struct lock_manager_operations lease_manager_ops = { /* * Initialize a lease, use the default lock manager operations */ -static int lease_init(struct file *filp, int type, struct file_lock *fl) +static int lease_init(struct file *filp, long type, struct file_lock *fl) { if (assign_type(fl, type) != 0) return -EINVAL; @@ -466,7 +466,7 @@ static int lease_init(struct file *filp, int type, struct file_lock *fl) } /* Allocate a file_lock initialised to this type of lease */ -static struct file_lock *lease_alloc(struct file *filp, int type) +static struct file_lock *lease_alloc(struct file *filp, long type) { struct file_lock *fl = locks_alloc_lock(); int error = -ENOMEM;