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Date:   Fri, 6 Jul 2018 15:55:15 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Kees Cook <keescook@chromium.org>
Cc:     osalvador@techadventures.net,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
        Oscar Salvador <osalvador@suse.de>
Subject: Re: [PATCH] fs, elf: Make sure to page align bss in
 load_elf_library
Message-Id: <20180706155515.f86d8394f8aae8bb841e2572@linux-foundation.org>
In-Reply-To: <CAGXu5jL4O_qwwAHmW1C8q77Jv1fe_1JCq6iFxC73VySBkvHSQw@mail.gmail.com>
References: <20180705145539.9627-1-osalvador@techadventures.net>
        <CAGXu5jL4O_qwwAHmW1C8q77Jv1fe_1JCq6iFxC73VySBkvHSQw@mail.gmail.com>
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On Thu, 5 Jul 2018 08:44:18 -0700 Kees Cook <keescook@chromium.org> wrote:

> On Thu, Jul 5, 2018 at 7:55 AM,  <osalvador@techadventures.net> wrote:
> > From: Oscar Salvador <osalvador@suse.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@suse.de>
> > Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> > Reported-by: syzbot+5dcb560fe12aa5091c06@syzkaller.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.