[PATCH 3.16 216/366] ALSA: opl3: Hardening for potential Spectre v1

Ben Hutchings
2018-10-14T23:12:06Z

From: Takashi Iwai <tiwai@suse.de>

commit 7f054a5bee0987f1e2d4e59daea462421c76f2cb upstream.

As recently Smatch suggested, one place in OPL3 driver may expand the
array directly from the user-space value with speculation:
sound/drivers/opl3/opl3_synth.c:476 snd_opl3_set_voice() warn: potential spectre issue 'snd_opl3_regmap'

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
sound/drivers/opl3/opl3_synth.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/sound/drivers/opl3/opl3_synth.c
+++ b/sound/drivers/opl3/opl3_synth.c
@@ -21,6 +21,7 @@

#include <linux/slab.h>
#include <linux/export.h>
+#include <linux/nospec.h>
#include <sound/opl3.h>
#include <sound/asound_fm.h>

@@ -448,7 +449,7 @@ static int snd_opl3_set_voice(struct snd
{
unsigned short reg_side;
unsigned char op_offset;
- unsigned char voice_offset;
+ unsigned char voice_offset, voice_op;

unsigned short opl3_reg;
unsigned char reg_val;
@@ -473,7 +474,9 @@ static int snd_opl3_set_voice(struct snd
voice_offset = voice->voice - MAX_OPL2_VOICES;
}
/* Get register offset of operator */
- op_offset = snd_opl3_regmap[voice_offset][voice->op];
+ voice_offset = array_index_nospec(voice_offset, MAX_OPL2_VOICES);
+ voice_op = array_index_nospec(voice->op, 4);
+ op_offset = snd_opl3_regmap[voice_offset][voice_op];

reg_val = 0x00;
/* Set amplitude modulation (tremolo) effect */