[PATCH 3.16 215/366] ALSA: hda: Hardening for potential Spectre v1

Ben Hutchings
2018-10-14T15:25:41Z

From: Takashi Iwai <tiwai@suse.de>

commit 69fa6f19b95597618ab30438a27b67ad93daa7c7 upstream.

As recently Smatch suggested, one place in HD-audio hwdep ioctl codes
may expand the array directly from the user-space value with
speculation:
sound/pci/hda/hda_local.h:467 get_wcaps() warn: potential spectre issue 'codec->wcaps'

As get_wcaps() itself is a fairly frequently called inline function,
and there is only one single call with a user-space value, we replace
only the latter one to open-code locally with array_index_nospec()
hardening in this patch.

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: s/core\.//g]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
sound/pci/hda/hda_hwdep.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

--- a/sound/pci/hda/hda_hwdep.c
+++ b/sound/pci/hda/hda_hwdep.c
@@ -21,6 +21,7 @@
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/compat.h>
+#include <linux/nospec.h>
#include <sound/core.h>
#include "hda_codec.h"
#include "hda_local.h"
@@ -51,7 +52,16 @@ static int get_wcap_ioctl(struct hda_cod

if (get_user(verb, &arg->verb))
return -EFAULT;
- res = get_wcaps(codec, verb >> 24);
+ /* open-code get_wcaps(verb>>24) with nospec */
+ verb >>= 24;
+ if (verb < codec->start_nid ||
+ verb >= codec->start_nid + codec->num_nodes) {
+ res = 0;
+ } else {
+ verb -= codec->start_nid;
+ verb = array_index_nospec(verb, codec->num_nodes);
+ res = codec->wcaps[verb];
+ }
if (put_user(res, &arg->res))
return -EFAULT;
return 0;