ALSA: rme9652: Fix potential Spectre v1 vulnerability
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Tue, 18 Dec 2018 17:18:34 +0000 (11:18 -0600)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 9 Jan 2019 16:14:46 +0000 (17:14 +0100)
commit076097b2847be84be34e70ae6f19690b28b2d122
tree9908f9ae6df707921d272e7d5521002207b4ea8d
parent9eb8b278cb191e8eaeb83eee17cff8cd37fcf0af
ALSA: rme9652: Fix potential Spectre v1 vulnerability

commit 0b84304ef5da92add8dc75a1b07879c5374cdb05 upstream.

info->channel 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/rme9652/hdsp.c:4100 snd_hdsp_channel_info() warn: potential spectre issue 'hdsp->channel_map' [r] (local cap)

Fix this by sanitizing info->channel before using it to index hdsp->channel_map

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].

Also, notice that I refactored the code a bit in order to get rid of the
following checkpatch warning:

ERROR: do not use assignment in if condition
FILE: sound/pci/rme9652/hdsp.c:4103:
if ((mapped_channel = hdsp->channel_map[info->channel]) < 0)

[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/rme9652/hdsp.c