From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx121.postini.com [74.125.245.121]) by kanga.kvack.org (Postfix) with SMTP id 29E9C6B0044 for ; Mon, 8 Oct 2012 11:15:56 -0400 (EDT) Date: Mon, 8 Oct 2012 11:15:52 -0400 From: Dave Jones Subject: Re: mpol_to_str revisited. Message-ID: <20121008151552.GA10881@redhat.com> References: <20121008150949.GA15130@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121008150949.GA15130@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Linux Kernel , bhutchings@solarflare.com, linux-mm@kvack.org, Linus Torvalds , Andrew Morton On Mon, Oct 08, 2012 at 11:09:49AM -0400, Dave Jones wrote: > Last month I sent in 80de7c3138ee9fd86a98696fd2cf7ad89b995d0a to remove > a user triggerable BUG in mempolicy. > > Ben Hutchings pointed out to me that my change introduced a potential leak > of stack contents to userspace, because none of the callers check the return value. > > This patch adds the missing return checking, and also clears the buffer beforehand. > > Reported-by: Ben Hutchings > Cc: stable@kernel.org > Signed-off-by: Dave Jones > > --- > unanswered question: why are the buffer sizes here different ? which is correct? A further unanswered question is how the state got so screwed up that we hit that default case at all. Looking at the original report: https://lkml.org/lkml/2012/9/6/356 What's in RAX looks suspiciously like left-over slab poison. If pol->mode was poisoned, that smells like we have a race where policy is getting freed while another process is reading it. Am I missing something, or is there no locking around that at all ? Dave -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org