ALSA: timer: Fix leak in events via snd_timer_user_ccallback

The stack object “r1” has a total size of 32 bytes. Its field
“event” and “val” both contain 4 bytes padding. These 8 bytes
padding bytes are sent to user without being initialized.
Signed-off-by: Kangjie Lu <kjlu@gatech.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
(cherry picked from commit 9a47e9cf)
CVE-2016-4578
BugLink: https://bugs.launchpad.net/bugs/1581866Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

sound/core/timer.c

@@ -1247,6 +1247,7 @@ static void snd_timer_user_ccallback(struct snd_timer_instance *timeri,
 		tu->tstamp = *tstamp;
 	if ((tu->filter & (1 << event)) == 0 || !tu->tread)
 		return;
+	memset(&r1, 0, sizeof(r1));
 	r1.event = event;
 	r1.tstamp = *tstamp;
 	r1.val = resolution;