From: Kees Cook <keescook@chromium.org>
To: Oleg Nesterov <oleg@redhat.com>
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: Tue, 12 Jul 2016 13:15:14 -0400 [thread overview]
Message-ID: <CAGXu5j+oZ49K0omm-7yMsR_kFYD-DQcYG8f+urS+TumzFYXR_w@mail.gmail.com> (raw)
In-Reply-To: <20160712133942.GA28837@redhat.com>
On Tue, Jul 12, 2016 at 9:39 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 07/11, Kees Cook wrote:
>>
>> On Mon, Jul 11, 2016 at 8:28 AM, Oleg Nesterov <oleg@redhat.com> wrote:
>> >
>> > and thus this patch fixes the error code returned by do_brk() in case
>> > of overflow, now it returns -ENOMEM rather than zero. Perhaps
>> >
>> > if (!len)
>> > return 0;
>> > len = PAGE_ALIGN(len);
>> > if (!len)
>> > return -ENOMEM;
>> >
>> > would be more clear but this is subjective.
>>
>> I'm fine either way.
>
> Me too, so feel free to ignore,
>
>> > I am wondering if we should shift this overflow check to the caller(s).
>> > Say, sys_brk() does find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE)
>> > before do_brk(), and in case of overflow find_vma_intersection() can
>> > wrongly return NULL.
>> >
>> > Then do_brk() will be called with len = -oldbrk, this can overflow or
>> > not but in any case this doesn't look right too.
>> >
>> > Or I am totally confused?
>>
>> I think the callers shouldn't request a negative value, sure, but
>> vm_brk should notice and refuse it.
>
> Not sure I understand...
>
> 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?
-Kees
--
Kees Cook
Chrome OS & Brillo Security
next prev parent reply other threads:[~2016-07-12 17:15 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 [this message]
2016-07-13 17:00 ` Oleg Nesterov
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