[PATCH] ALSA: hda/hdmi: fix incorrect locking in hdmi_pcm_close

[Takashi Iwai]

On Tue, 13 Oct 2020 17:26:28 +0200,
Kai Vehmanen wrote:
> 
> 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 at linux.intel.com>

Applied now.  Thanks.


Takashi