linux-kernel - Re: [PATCH] ALSA: emux_hwdep: Fix potential Spectre v1 vulnerabilities

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Date:   Thu, 13 Dec 2018 09:13:44 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     " Gustavo A. R. Silva " <gustavo@...eddedor.com>
Cc:     "Jaroslav Kysela" <perex@...ex.cz>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: emux_hwdep: Fix potential Spectre v1 vulnerabilities

On Wed, 12 Dec 2018 18:20:49 +0100,
 Gustavo A. R. Silva  wrote:
> 
> info.mode and info.port are indirectly controlled by user-space,
> hence leading to a potential exploitation of the Spectre variant 1
> vulnerability.
> 
> These issues were detected with the help of Smatch:
> 
> sound/synth/emux/emux_hwdep.c:72 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs[i]->ctrls' [w] (local cap)
> sound/synth/emux/emux_hwdep.c:75 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs' [w] (local cap)
> sound/synth/emux/emux_hwdep.c:75 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs[info.port]->ctrls' [w] (local cap)
> 
> Fix this by sanitizing both info.mode and info.port before using them
> to index emu->portptrs[i]->ctrls, emu->portptrs[info.port]->ctrls and
> emu->portptrs.
> 
> Notice that given that speculation windows are large, the policy is
> to kill the speculation on the first load and not worry if it can be
> completed with a dependent load/store [1].
> 
> [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Applied now (with moving the linux/nospec.h in a more appropriate
line).


thanks,

Takashi