Commit c4d65a3a authored Dec 18, 2018 by Gustavo A. R. Silva Committed by Greg Kroah-Hartman Jan 09, 2019

ALSA: emu10k1: Fix potential Spectre v1 vulnerabilities

commit 5ae4f61f012a097df93de2285070ec8e34716d29 upstream.

ipcm->substream 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/pci/emu10k1/emufx.c:1031 snd_emu10k1_ipcm_poke() warn: potential spectre issue 'emu->fx8010.pcm' [r] (local cap)
sound/pci/emu10k1/emufx.c:1075 snd_emu10k1_ipcm_peek() warn: potential spectre issue 'emu->fx8010.pcm' [r] (local cap)

Fix this by sanitizing ipcm->substream before using it to index emu->fx8010.pcm

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 076097b2

sound/pci/emu10k1/emufx.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -36,6 +36,7 @@
		#include <linux/init.h>
		#include <linux/mutex.h>
		#include <linux/moduleparam.h>
		#include <linux/nospec.h>

		#include <sound/core.h>
		#include <sound/tlv.h>
		@@ -1033,6 +1034,8 @@ static int snd_emu10k1_ipcm_poke(struct snd_emu10k1 *emu,

		if (ipcm->substream >= EMU10K1_FX8010_PCM_COUNT)
		return -EINVAL;
		ipcm->substream = array_index_nospec(ipcm->substream,
		EMU10K1_FX8010_PCM_COUNT);
		if (ipcm->channels > 32)
		return -EINVAL;
		pcm = &emu->fx8010.pcm[ipcm->substream];
		@@ -1079,6 +1082,8 @@ static int snd_emu10k1_ipcm_peek(struct snd_emu10k1 *emu,

		if (ipcm->substream >= EMU10K1_FX8010_PCM_COUNT)
		return -EINVAL;
		ipcm->substream = array_index_nospec(ipcm->substream,
		EMU10K1_FX8010_PCM_COUNT);
		pcm = &emu->fx8010.pcm[ipcm->substream];
		mutex_lock(&emu->fx8010.lock);
		spin_lock_irq(&emu->reg_lock);