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    Subject[PATCH 5.8 029/633] ALSA: hda/hdmi: fix incorrect locking in hdmi_pcm_close
    Date
    From: Kai Vehmanen <kai.vehmanen@linux.intel.com>

    commit ce1558c285f9ad04c03b46833a028230771cc0a7 upstream.

    A race exists between closing a PCM and update of ELD data. In
    hdmi_pcm_close(), hinfo->nid value is modified without taking
    spec->pcm_lock. If this happens concurrently while processing an ELD
    update in hdmi_pcm_setup_pin(), converter assignment may be done
    incorrectly.

    This bug was found by hitting a WARN_ON in snd_hda_spdif_ctls_assign()
    in a HDMI receiver connection stress test:

    [2739.684569] WARNING: CPU: 5 PID: 2090 at sound/pci/hda/patch_hdmi.c:1898 check_non_pcm_per_cvt+0x41/0x50 [snd_hda_codec_hdmi]
    ...
    [2739.684707] Call Trace:
    [2739.684720] update_eld+0x121/0x5a0 [snd_hda_codec_hdmi]
    [2739.684736] hdmi_present_sense+0x21e/0x3b0 [snd_hda_codec_hdmi]
    [2739.684750] check_presence_and_report+0x81/0xd0 [snd_hda_codec_hdmi]
    [2739.684842] intel_audio_codec_enable+0x122/0x190 [i915]

    Fixes: 42b2987079ec ("ALSA: hda - hdmi playback without monitor in dynamic pcm bind mode")
    Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
    Cc: <stable@vger.kernel.org>
    Link: https://lore.kernel.org/r/20201013152628.920764-1-kai.vehmanen@linux.intel.com
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    sound/pci/hda/patch_hdmi.c | 20 ++++++++++++--------
    1 file changed, 12 insertions(+), 8 deletions(-)

    --- a/sound/pci/hda/patch_hdmi.c
    +++ b/sound/pci/hda/patch_hdmi.c
    @@ -1989,22 +1989,25 @@ static int hdmi_pcm_close(struct hda_pcm
    int pinctl;
    int err = 0;

    + mutex_lock(&spec->pcm_lock);
    if (hinfo->nid) {
    pcm_idx = hinfo_to_pcm_index(codec, hinfo);
    - if (snd_BUG_ON(pcm_idx < 0))
    - return -EINVAL;
    + if (snd_BUG_ON(pcm_idx < 0)) {
    + err = -EINVAL;
    + goto unlock;
    + }
    cvt_idx = cvt_nid_to_cvt_index(codec, hinfo->nid);
    - if (snd_BUG_ON(cvt_idx < 0))
    - return -EINVAL;
    + if (snd_BUG_ON(cvt_idx < 0)) {
    + err = -EINVAL;
    + goto unlock;
    + }
    per_cvt = get_cvt(spec, cvt_idx);
    -
    snd_BUG_ON(!per_cvt->assigned);
    per_cvt->assigned = 0;
    hinfo->nid = 0;

    azx_stream(get_azx_dev(substream))->stripe = 0;

    - mutex_lock(&spec->pcm_lock);
    snd_hda_spdif_ctls_unassign(codec, pcm_idx);
    clear_bit(pcm_idx, &spec->pcm_in_use);
    pin_idx = hinfo_to_pin_index(codec, hinfo);
    @@ -2034,10 +2037,11 @@ static int hdmi_pcm_close(struct hda_pcm
    per_pin->setup = false;
    per_pin->channels = 0;
    mutex_unlock(&per_pin->lock);
    - unlock:
    - mutex_unlock(&spec->pcm_lock);
    }

    +unlock:
    + mutex_unlock(&spec->pcm_lock);
    +
    return err;
    }


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