linux-kernel - Re: [PATCH 01/11] media: tm6000: fix potential Spectre variant 1

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]

Date:   Tue, 24 Apr 2018 13:21:29 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] media: tm6000: fix potential Spectre variant 1

On Tue, Apr 24, 2018 at 12:36:09PM +0200, Peter Zijlstra wrote:
> 
> Then usespace probes which part of the descr[] array is now in cache and
> from that it can infer the initial out-of-bound value.

Just had a better look at v4l_fill_fmtdesc() and actually read the
comment. The code cannot be compiled as a array because it is big and
sparse. But the log(n) condition tree is a prime candidate for the
branchscope side-channel, which would be able to reconstruct a
significant number of bits of the original value. A denser tree gives
more bits etc.