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    Subject[PATCH 4.9 037/172] ALSA: hda - Fix endless loop of codec configure
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Takashi Iwai <tiwai@suse.de>

    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@ffwll.ch>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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 */
    #define HDA_RW_NO_RESPONSE_FALLBACK (1 << 0)
    --- 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) {
    snd_hda_codec_configure(codec);
    }
    return 0;

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