ALSA: emu10k1: Fix potential Spectre v1 vulnerabilities
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Tue, 18 Dec 2018 17:52:16 +0000 (11:52 -0600)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 9 Jan 2019 16:14:46 +0000 (17:14 +0100)
commitc4d65a3afd071608e1b9b86112a4f0cf01932e4d
treea2488320a5782bef23db1b8857de4330eca48357
parent076097b2847be84be34e70ae6f19690b28b2d122
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>
sound/pci/emu10k1/emufx.c