Commit 2b1d9c8f authored Mar 20, 2019 by Gustavo A. R. Silva Committed by Takashi Iwai Mar 21, 2019

ALSA: rawmidi: Fix potential Spectre v1 vulnerability

info->stream 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/core/rawmidi.c:604 __snd_rawmidi_info_select() warn: potential spectre issue 'rmidi->streams' [r] (local cap)

Fix this by sanitizing info->stream before using it to index
rmidi->streams.

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://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/



Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 667a8f73

sound/core/rawmidi.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -30,6 +30,7 @@
		#include <linux/module.h>
		#include <linux/delay.h>
		#include <linux/mm.h>
		#include <linux/nospec.h>
		#include <sound/rawmidi.h>
		#include <sound/info.h>
		#include <sound/control.h>
		@@ -601,6 +602,7 @@ static int __snd_rawmidi_info_select(struct snd_card *card,
		return -ENXIO;
		if (info->stream < 0 \|\| info->stream > 1)
		return -EINVAL;
		info->stream = array_index_nospec(info->stream, 2);
		pstr = &rmidi->streams[info->stream];
		if (pstr->substream_count == 0)
		return -ENOENT;

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