[PATCH 4.2.y-ckt 012/218] ALSA: usb-audio: Add sanity checks for endpoint accesses

[Kamal Mostafa]

4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Takashi Iwai <tiwai@xxxxxxx>

commit 447d6275f0c21f6cc97a88b3a0c601436a4cdf2a upstream.

Add some sanity check codes before actually accessing the endpoint via
get_endpoint() in order to avoid the invalid access through a
malformed USB descriptor.  Mostly just checking bNumEndpoints, but in
one place (snd_microii_spdif_default_get()), the validity of iface and
altsetting index is checked as well.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=971125
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 sound/usb/clock.c        | 2 ++
 sound/usb/endpoint.c     | 3 +++
 sound/usb/mixer_quirks.c | 4 ++++
 sound/usb/pcm.c          | 2 ++
 4 files changed, 11 insertions(+)

diff --git a/sound/usb/clock.c b/sound/usb/clock.c
index 2ed260b..7ccbcaf 100644
--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -285,6 +285,8 @@ static int set_sample_rate_v1(struct snd_usb_audio *chip, int iface,
 	unsigned char data[3];
 	int err, crate;
 
+	if (get_iface_desc(alts)->bNumEndpoints < 1)
+		return -EINVAL;
 	ep = get_endpoint(alts, 0)->bEndpointAddress;
 
 	/* if endpoint doesn't have sampling rate control, bail out */
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 03b0744..e7f470a 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -413,6 +413,9 @@ exit_clear:
  *
  * New endpoints will be added to chip->ep_list and must be freed by
  * calling snd_usb_endpoint_free().
+ *
+ * For SND_USB_ENDPOINT_TYPE_SYNC, the caller needs to guarantee that
+ * bNumEndpoints > 1 beforehand.
  */
 struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
 					      struct usb_host_interface *alts,
diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index db9547d..f8ffcda4 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -1532,7 +1532,11 @@ static int snd_microii_spdif_default_get(struct snd_kcontrol *kcontrol,
 
 	/* use known values for that card: interface#1 altsetting#1 */
 	iface = usb_ifnum_to_if(chip->dev, 1);
+	if (!iface || iface->num_altsetting < 2)
+		return -EINVAL;
 	alts = &iface->altsetting[1];
+	if (get_iface_desc(alts)->bNumEndpoints < 1)
+		return -EINVAL;
 	ep = get_endpoint(alts, 0)->bEndpointAddress;
 
 	err = snd_usb_ctl_msg(chip->dev,
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index b4ef410..cbb9325 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -159,6 +159,8 @@ static int init_pitch_v1(struct snd_usb_audio *chip, int iface,
 	unsigned char data[1];
 	int err;
 
+	if (get_iface_desc(alts)->bNumEndpoints < 1)
+		return -EINVAL;
 	ep = get_endpoint(alts, 0)->bEndpointAddress;
 
 	data[0] = 1;
-- 
2.7.4