From: Oleg Nesterov <oleg@redhat.com>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hector Marco-Gisbert <hecmargi@upv.es>,
Ismael Ripoll Ripoll <iripoll@upv.es>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Chen Gang <gang.chen.5i5j@gmail.com>,
Michal Hocko <mhocko@suse.com>,
Konstantin Khlebnikov <koct9i@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm: refuse wrapped vm_brk requests
Date: Wed, 13 Jul 2016 19:00:49 +0200 [thread overview]
Message-ID: <20160713170048.GA24553@redhat.com> (raw)
In-Reply-To: <CAGXu5j+oZ49K0omm-7yMsR_kFYD-DQcYG8f+urS+TumzFYXR_w@mail.gmail.com>
On 07/12, Kees Cook wrote:
>
> On Tue, Jul 12, 2016 at 9:39 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > I tried to say that, with or without this change, sys_brk() should check
> > for overflow too, otherwise it looks buggy.
>
> Hmm, it's not clear to me the right way to fix sys_brk(), but it looks
> like my change to do_brk() would catch the problem?
How?
Once again, afaics nothing bad can happen, sys_brk() will silently fail,
just the code looks wrong anyway.
Suppose that newbrk == 0 due to overflow, then both
if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
goto out;
and
if (do_brk(oldbrk, newbrk-oldbrk) < 0)
goto out;
look buggy.
find_vma_intersection(start_addr, end_addr) expects that start_addr < end_addr.
Again, we do not really care if it returns NULL or not, and newbrk == 0 just
means it will certainly return NULL if there is something above oldbrk. Just
looks buggy/confusing.
do_brk(0 - oldbrk) will fail and this is what we want. But not because
your change will catch the problem, PAGE_ALIGNE(-oldbrk) won't necessarily
overflow. However, -oldbrk > TASK_SIZE so get_unmapped_area() should fail.
Nevermind, this is almost off-topic, so let me repeat just in case that
both patches look good to me.
Oleg.
prev parent reply other threads:[~2016-07-13 17:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-08 21:48 [PATCH 0/2] binfmt_elf: fix calculations for bss padding Kees Cook
2016-07-08 21:48 ` [PATCH 1/2] " Kees Cook
2016-07-12 22:32 ` Kees Cook
2016-07-08 21:48 ` [PATCH 2/2] mm: refuse wrapped vm_brk requests Kees Cook
2016-07-11 12:28 ` Oleg Nesterov
2016-07-11 18:01 ` Kees Cook
2016-07-12 13:39 ` Oleg Nesterov
2016-07-12 17:15 ` Kees Cook
2016-07-13 17:00 ` Oleg Nesterov [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160713170048.GA24553@redhat.com \
--to=oleg@redhat.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=aryabinin@virtuozzo.com \
--cc=gang.chen.5i5j@gmail.com \
--cc=hecmargi@upv.es \
--cc=iripoll@upv.es \
--cc=keescook@chromium.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=koct9i@gmail.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).