5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Shuangpeng Bai <redacted>
commit fc530fe168bb2b745a93f553ad21fc25fd9cba3d upstream.
The ALSA PCM callbacks store the driver state in pcm->private_data. An
open PCM file can outlive USB disconnect because usbtv_audio_free() uses
snd_card_free_when_closed(). The disconnect path can then drop the V4L2
device reference and free struct usbtv before ALSA releases the substream,
so a later close dereferences freed memory in snd_usbtv_pcm_close().
Take a V4L2 device reference for the ALSA card and drop it from the card
private_free callback. This keeps struct usbtv valid until ALSA has closed
the remaining files and freed the card.
Closes: https://lore.kernel.org/r/178144969601.60470.4852887710381872458@gmail.com (local)
Fixes: 63ddf68de52e ("[media] usbtv: add audio support")
Cc: <redacted>
Signed-off-by: Shuangpeng Bai <redacted>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/media/usb/usbtv/usbtv-audio.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--- a/drivers/media/usb/usbtv/usbtv-audio.c
+++ b/drivers/media/usb/usbtv/usbtv-audio.c
@@ -317,6 +317,13 @@ static const struct snd_pcm_ops snd_usbt
.pointer = snd_usbtv_pointer,
};
+static void usbtv_audio_card_free(struct snd_card *card)
+{
+ struct usbtv *usbtv = card->private_data;
+
+ v4l2_device_put(&usbtv->v4l2_dev);
+}
+
int usbtv_audio_init(struct usbtv *usbtv)
{
int rv;@@ -331,6 +338,10 @@ int usbtv_audio_init(struct usbtv *usbtv
if (rv < 0)
return rv;
+ v4l2_device_get(&usbtv->v4l2_dev);
+ card->private_data = usbtv;
+ card->private_free = usbtv_audio_card_free;
+
strscpy(card->driver, usbtv->dev->driver->name, sizeof(card->driver));
strscpy(card->shortname, "usbtv", sizeof(card->shortname));
snprintf(card->longname, sizeof(card->longname),