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

[Takashi Iwai <tiwai@suse.de>]

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@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

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


thanks,

Takashi