linux-kernel - Re: [PATCH] mm/slab_common.c: fix possible spectre-v1 in kmalloc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAFbcbMAKOSjZzCumK3iGxBGL1Bjf+Qx==87F8A9xPBy5msj+Dw@mail.gmail.com>
Date:   Thu, 30 May 2019 13:21:23 +0800
From:   Dianzhang Chen <dianzhangchen0@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/slab_common.c: fix possible spectre-v1 in kmalloc_slab()

thanks, i think your suggestion is ok.
in my previous method is easy to understand for spectre  logic,
but your suggestion is more sense to use of array_index_nospec.



On Thu, May 30, 2019 at 3:48 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Wed, May 29, 2019 at 08:37:28PM +0800, Dianzhang Chen wrote:
> > The `size` in kmalloc_slab() is indirectly controlled by userspace via syscall: poll(defined in fs/select.c), hence leading to a potential exploitation of the Spectre variant 1 vulnerability.
> > The `size` can be controlled from: poll -> do_sys_poll -> kmalloc -> __kmalloc -> kmalloc_slab.
> >
> > Fix this by sanitizing `size` before using it to index size_index.
>
> I think it makes more sense to sanitize size in size_index_elem(),
> don't you?
>
>  static inline unsigned int size_index_elem(unsigned int bytes)
>  {
> -       return (bytes - 1) / 8;
> +       return array_index_nospec((bytes - 1) / 8, ARRAY_SIZE(size_index));
>  }
>
> (untested)