From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pat Erley Subject: Re: Possible regression from "fs/exec.c: call arch_pick_mmap_layout() only once" Date: Thu, 02 Jan 2014 16:39:51 -0600 Message-ID: <52C5EAB7.9030003@erley.org> References: <52C5DD07.40208@erley.org> <2300703.z3jyM3yTZv@sandpuppy> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from erley.org ([97.107.129.9]:52382 "EHLO remote.erley.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751084AbaABWkM (ORCPT ); Thu, 2 Jan 2014 17:40:12 -0500 In-Reply-To: <2300703.z3jyM3yTZv@sandpuppy> Sender: linux-next-owner@vger.kernel.org List-ID: To: Richard Weinberger Cc: linux-next@vger.kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org On 01/02/2014 04:24 PM, Richard Weinberger wrote: > Am Donnerstag, 2. Januar 2014, 15:41:27 schrieb Pat Erley: >> On my 64bit kernel, commit 283fe963095b38a6ab75dda1436ee66b9e45c7c2 >> seems to have broken 32bit compatibility. I've run the bisection twice, >> and verified that reverting this on HEAD fixes the problem. I've >> uploaded my .config to pastebin at http://pastebin.com/kVcr9H65 >> >> Even this simple program: >> >> main(){puts("HELLO");} >> >> compiled with: >> >> gcc -m32 test.c >> >> Will crash with a segfault. Stracing shows that it's failing to >> allocate memory. > > Good catch! > > flush_old_exec() is called before setup_new_exec() and I've removed > arch_pick_mmap_layout() from the second call site. > Which turned out to be wrong. > > It is wrong because between both callers current->personality is changed. > So, we have to remove the first call to arch_pick_mmap_layout() and keep the > latter because only then the correct personality is set up. > > Can you please test your config with the following patch applied and having > 283fe96 reverted? > > If it works out for you I'd send an updated patch to Andrew. > In the meanwhile I'll double check all call sites... > > Thanks, > //richard > > --- > diff --git a/fs/exec.c b/fs/exec.c > index 7ea097f..a733599 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -843,7 +843,6 @@ static int exec_mmap(struct mm_struct *mm) > tsk->active_mm = mm; > activate_mm(active_mm, mm); > task_unlock(tsk); > - arch_pick_mmap_layout(mm); > if (old_mm) { > up_read(&old_mm->mmap_sem); > BUG_ON(active_mm != old_mm); > Compiling right now. Will test later tonight and let you know. Pat