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: 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>

diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 0ffbfcb91256f4a8d57cb656ee0b0ae8080b1db1..ccd1df05965404f6f8ab127c39806f08981862ff 100644 (file)
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -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);
@@ -2091,10 +2094,11 @@ 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);
        }
 
+unlock:
+       mutex_unlock(&spec->pcm_lock);
+
        return err;
 }