media: usbtv: keep device alive while ALSA card exists

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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
Fixes: 63ddf68de5 ("[media] usbtv: add audio support")
Cc: stable@vger.kernel.org
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

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Shuangpeng Bai 2026-07-06 16:24:06 -04:00 • committed by Hans Verkuil

parent 76e379754b

commit fc530fe168

1 changed files with 11 additions and 0 deletions

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drivers/media/usb/usbtv/usbtv-audio.c

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