linux-kernel - Re: [PATCH] fs, elf: Make sure to page align bss in load_elf

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Date:   Fri, 6 Jul 2018 15:55:15 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     osalvador@...hadventures.net,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH] fs, elf: Make sure to page align bss in
 load_elf_library

On Thu, 5 Jul 2018 08:44:18 -0700 Kees Cook <keescook@...omium.org> wrote:

> On Thu, Jul 5, 2018 at 7:55 AM,  <osalvador@...hadventures.net> wrote:
> > From: Oscar Salvador <osalvador@...e.de>
> >
> > The current code does not make sure to page align bss before calling
> > vm_brk(), and this can lead to a VM_BUG_ON() in __mm_populate()
> > due to the requested lenght not being correctly aligned.
> >
> > Let us make sure to align it properly.
> >
> > Signed-off-by: Oscar Salvador <osalvador@...e.de>
> > Tested-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
> > Reported-by: syzbot+5dcb560fe12aa5091c06@...kaller.appspotmail.com
> 
> Wow. CONFIG_USELIB? I'm surprised distros are still using this. 32-bit
> only, and libc5 and earlier only.

Presumably doesn't happen much, but people who *are* enabling this will
want the fix, so I added the cc:stable.