[PATCH 4.9 037/172] ALSA: hda - Fix endless loop of codec configure

From: Greg Kroah-Hartman
Date: Mon Jul 03 2017 - 10:37:49 EST

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


From: Takashi Iwai <tiwai@xxxxxxx>

commit d94815f917da770d42c377786dc428f542e38f71 upstream.

azx_codec_configure() loops over the codecs found on the given
controller via a linked list. The code used to work in the past, but
in the current version, this may lead to an endless loop when a codec
binding returns an error.

The culprit is that the snd_hda_codec_configure() unregisters the
device upon error, and this eventually deletes the given codec object
from the bus. Since the list is initialized via list_del_init(), the
next object points to the same device itself. This behavior change
was introduced at splitting the HD-audio code code, and forgotten to
adapt it here.

For fixing this bug, just use a *_safe() version of list iteration.

Fixes: d068ebc25e6e ("ALSA: hda - Move some codes up to hdac_bus struct")
Reported-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

sound/pci/hda/hda_codec.h | 2 ++
sound/pci/hda/hda_controller.c | 8 ++++++--
2 files changed, 8 insertions(+), 2 deletions(-)

--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -294,6 +294,8 @@ struct hda_codec {

#define list_for_each_codec(c, bus) \
list_for_each_entry(c, &(bus)->core.codec_list, core.list)
+#define list_for_each_codec_safe(c, n, bus) \
+ list_for_each_entry_safe(c, n, &(bus)->core.codec_list, core.list)

/* snd_hda_codec_read/write optional flags */
--- a/sound/pci/hda/hda_controller.c
+++ b/sound/pci/hda/hda_controller.c
@@ -1333,8 +1333,12 @@ EXPORT_SYMBOL_GPL(azx_probe_codecs);
/* configure each codec instance */
int azx_codec_configure(struct azx *chip)
- struct hda_codec *codec;
- list_for_each_codec(codec, &chip->bus) {
+ struct hda_codec *codec, *next;
+ /* use _safe version here since snd_hda_codec_configure() deregisters
+ * the device upon error and deletes itself from the bus list.
+ */
+ list_for_each_codec_safe(codec, next, &chip->bus) {
return 0;