From: Jaroslav Kysela <jkysela@redhat.com>
Date: Mon, 22 Mar 2010 17:15:51 -0400
Subject: [sound] hda_intel: avoid divide by zero in azx devices
Message-id: <201003221715.o2MHFpqI024531@int-mx08.intmail.prod.int.phx2.redhat.com>
Patchwork-id: 23696
O-Subject: [RHEL 5.6 PATCH] ALSA - snd-hda-intel driver - avoid divide by zero
Bugzilla: 567172
RH-Acked-by: Jarod Wilson <jarod@redhat.com>
RH-Acked-by: Jerome Marchand <jmarchan@redhat.com>
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>

Bugzilla
========
BZ#567172
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=567172

Description
===========
The OSS emulation in the ALSA driver can trigger division by zero
in the snd-hda-intel driver. This patch adds a simple check for this
situation to the snd-hda-intel driver.

This version contains WARN_ONCE-like code.

Upstream Status of the patch
============================
In upstream.

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 0541b7c..901b5ad 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -1857,6 +1857,15 @@ static int azx_position_ok(struct azx *chip, struct azx_dev *azx_dev)
 
 	if (!bdl_pos_adj[chip->dev_index])
 		return 1; /* no delayed ack */
+	if (azx_dev->period_bytes == 0) {
+		static int once;
+		if (!once)
+			printk(KERN_WARNING
+			       "hda-intel: Divide by zero was avoided "
+			       "in azx_dev->period_bytes.\n");
+		once = 1;
+		return 0;
+	}
 	if (pos % azx_dev->period_bytes > azx_dev->period_bytes / 2)
 		return 0; /* NG - it's below the period boundary */
 	return 1; /* OK, it's fine */