Re: [PATCH] ALSA: isa/wavefront: Fix potential Spectre v1 vulnerabilities

From: Gustavo A. R. Silva
Date: Thu Dec 20 2018 - 12:13:35 EST

On 12/20/18 2:11 AM, Takashi Iwai wrote:
On Thu, 20 Dec 2018 00:31:43 +0100,
Gustavo A. R. Silva wrote:

header->number is indirectly controlled by user-space, hence leading
to a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

sound/isa/wavefront/wavefront_synth.c:792 wavefront_send_patch() warn: potential spectre issue 'dev->patch_status' [w] (local cap)
sound/isa/wavefront/wavefront_synth.c:819 wavefront_send_program() warn: potential spectre issue 'dev->prog_status' [w] (local cap)
sound/isa/wavefront/wavefront_synth.c:1197 wavefront_send_alias() warn: potential spectre issue 'dev->sample_status' [w]
sound/isa/wavefront/wavefront_synth.c:1248 wavefront_send_multisample() warn: potential spectre issue 'dev->sample_status' [w]
sound/isa/wavefront/wavefront_synth.c:1548 wavefront_synth_control() warn: potential spectre issue 'dev->sample_status' [r] (local cap)

Fix this by sanitizing header->number before using it to index
dev->patch_status, dev->prog_status and dev->sample_status.

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].


Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>

Is there any platform with ISA slot that suffers from Spectre?

Do you mean 'any other'?

If so, yeah, I just spotted some Spectre vulns in sound/isa/sb/emu8000.c

I'll send a patch for that.