ALSA: hda-intel: Avoid divide by zero crash

On my AMD780V chipset, hda_intel.c can crash the kernel with a divide by zero for as-yet unknown reasons. A simple check for zero prevents it, though the problem that causes it remains. Since the workaround is harmless and won't affect anyone except victims of this bug, it should be safe; moreover, because this crash can be triggered by a user-mode application, there are denial of service implications on the systems affected by the bug without the patch. Signed-off-by: Jody Bruchon <[email protected]> Cc: <[email protected]> Signed-off-by: Takashi Iwai <[email protected]>
mrcsosa · Feb 9, 2010 · fed08d0 · fed08d0
1 parent 9492837
commit fed08d0
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
@@ -1893,6 +1893,12 @@ 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) {
+		printk(KERN_WARNING
+		       "hda-intel: Divide by zero was avoided "
+		       "in azx_dev->period_bytes.\n");
+		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 */