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ALSA: emu10k1: Fix potential Spectre v1 vulnerabilities

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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>
This commit is contained in:
Gustavo A. R. Silva 2018-12-18 11:52:16 -06:00 committed by Takashi Iwai
parent 0b84304ef5
commit 5ae4f61f01
1 changed files with 5 additions and 0 deletions
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5
sound/pci/emu10k1/emufx.c
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@ -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>
@ -1026,6 +1027,8 @@ 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];
@ -1072,6 +1075,8 @@ 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);