[PATCH 5.8 029/633] ALSA: hda/hdmi: fix incorrect locking in hdmi_pcm_close

Greg Kroah-Hartman
2020-10-27T17:09:13Z

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;
}