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-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm: refuse wrapped vm_brk requests
Date: Mon, 11 Jul 2016 14:28:26 +0200 [thread overview]
Message-ID: <20160711122826.GA969@redhat.com> (raw)
In-Reply-To: <1468014494-25291-3-git-send-email-keescook@chromium.org>
I think both patches are fine, just a question.
On 07/08, Kees Cook wrote:
>
> -static int do_brk(unsigned long addr, unsigned long len)
> +static int do_brk(unsigned long addr, unsigned long request)
> {
> struct mm_struct *mm = current->mm;
> struct vm_area_struct *vma, *prev;
> - unsigned long flags;
> + unsigned long flags, len;
> struct rb_node **rb_link, *rb_parent;
> pgoff_t pgoff = addr >> PAGE_SHIFT;
> int error;
>
> - len = PAGE_ALIGN(len);
> + len = PAGE_ALIGN(request);
> + if (len < request)
> + return -ENOMEM;
So iiuc "len < request" is only possible if len == 0, right?
> if (!len)
> return 0;
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 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?
Oleg.
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next prev parent reply other threads:[~2016-07-11 12:28 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 [this message]
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
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