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Mon, 06 Jul 2026 13:25:14 -0700 (PDT) From: Shuangpeng Bai To: mchehab@kernel.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Shuangpeng Bai Subject: [PATCH] media: usbtv: keep device alive while ALSA card exists Date: Mon, 6 Jul 2026 16:24:06 -0400 Message-ID: <20260706202406.1381177-1-shuangpeng.kernel@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178144969601.60470.4852887710381872458@gmail.com> References: <178144969601.60470.4852887710381872458@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: 63ddf68de52e ("[media] usbtv: add audio support") Signed-off-by: Shuangpeng Bai --- drivers/media/usb/usbtv/usbtv-audio.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/media/usb/usbtv/usbtv-audio.c b/drivers/media/usb/usbtv/usbtv-audio.c index 333bd305a4f9..ae0a14e5ed2a 100644 --- 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_usbtv_pcm_ops = { .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), -- 2.43.0