[PATCH 3.16 220/366] ALSA: rme9652: Hardening for potential Spectre v1

Ben Hutchings
2018-10-14T23:12:07Z

From: Takashi Iwai <tiwai@suse.de>

commit f526afcd8f71945c23ce581d7864ace93de8a4f7 upstream.

As recently Smatch suggested, one place in RME9652 driver may expand
the array directly from the user-space value with speculation:
sound/pci/rme9652/rme9652.c:2074 snd_rme9652_channel_info() warn: potential spectre issue 'rme9652->channel_map' (local cap)

This patch puts array_index_nospec() for hardening against it.

BugLink: https://marc.info/?l=linux-kernel&m=152411496503418&w=2
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
sound/pci/rme9652/rme9652.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/sound/pci/rme9652/rme9652.c
+++ b/sound/pci/rme9652/rme9652.c
@@ -35,6 +35,7 @@

#include <asm/current.h>
#include <asm/io.h>
+#include <linux/nospec.h>

static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; /* Index 0-MAX */
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; /* ID for this card */
@@ -2059,9 +2060,10 @@ static int snd_rme9652_channel_info(stru
if (snd_BUG_ON(info->channel >= RME9652_NCHANNELS))
return -EINVAL;

- if ((chn = rme9652->channel_map[info->channel]) < 0) {
+ chn = rme9652->channel_map[array_index_nospec(info->channel,
+ RME9652_NCHANNELS)];
+ if (chn < 0)
return -EINVAL;
- }

info->offset = chn * RME9652_CHANNEL_BUFFER_BYTES;
info->first = 0;