Commit ce1558c2 authored Oct 13, 2020 by Kai Vehmanen Committed by Takashi Iwai Oct 13, 2020

ALSA: hda/hdmi: fix incorrect locking in hdmi_pcm_close



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: 42b29870 ("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>

parent f401b2c9

sound/pci/hda/patch_hdmi.c

+12 −8

Original line number	Diff line number	Diff line
		@@ -2046,22 +2046,25 @@ static int hdmi_pcm_close(struct hda_pcm_stream *hinfo,
		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);
		@@ -2091,9 +2094,10 @@ static int hdmi_pcm_close(struct hda_pcm_stream *hinfo,
		per_pin->setup = false;
		per_pin->channels = 0;
		mutex_unlock(&per_pin->lock);
		}

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

		return err;
		}

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