[PATCH 3.18 37/47] ALSA: usb-audio: Fix an out-of-bound read in create_composite_quirks

[Greg Kroah-Hartman]

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

------------------

From: Hui Peng <benquike@xxxxxxx>

commit cbb2ebf70daf7f7d97d3811a2ff8e39655b8c184 upstream.

In `create_composite_quirk`, the terminating condition of for loops is
`quirk->ifnum < 0`. So any composite quirks should end with `struct
snd_usb_audio_quirk` object with ifnum < 0.

    for (quirk = quirk_comp->data; quirk->ifnum >= 0; ++quirk) {

    	.....
    }

the data field of Bower's & Wilkins PX headphones usb device device quirks
do not end with {.ifnum = -1}, wihch may result in out-of-bound read.

This Patch fix the bug by adding an ending quirk object.

Fixes: 240a8af929c7 ("ALSA: usb-audio: Add a quirck for B&W PX headphones")
Signed-off-by: Hui Peng <benquike@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 sound/usb/quirks-table.h |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -3356,6 +3356,9 @@ AU0828_DEVICE(0x2040, 0x7270, "Hauppauge
 					}
 				}
 			},
+			{
+				.ifnum = -1
+			},
 		}
 	}
 },