linux-kernel - Re: [PATCH] media: dvb-usb: fix memory leak in cinergyt2_frontend

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Date:   Wed, 11 Aug 2021 22:54:21 +0100
From:   Sean Young <sean@...s.org>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     mchehab@...nel.org, tomimo@...rcle.nullnet.fi,
        thierry.merle@...e.fr, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] media: dvb-usb: fix memory leak in
 cinergyt2_frontend_attach

On Sun, Jun 20, 2021 at 11:23:17PM +0300, Pavel Skripkin wrote:
> My local syzbot instance hit a memory leak in
> cinergyt2_frontend_attach() [1].
> 
> The problem was in non-freed dvb_frontend in case of error.
> If dvb_usb_generic_rw() call fails, an error will be returned from
> cinergyt2_frontend_attach() [1] and num_adapters_initialized of
> dvb_usb_device won't be incremented. That means dvb usb library
> won't take care of freeing allocated frontend.

This issue is already fixed by:

9ad1efee086e0 media: dvd_usb: memory leak in cinergyt2_fe_attach

Thanks for reporting and making a patch though.


Sean

> 
> Fail log:
> BUG: memory leak
> unreferenced object 0xffff88801d9c6000 (size 2048):
>   comm "kworker/1:3", pid 2960, jiffies 4295150569 (age 17.150s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 54 65 72 72 61 54 65 63  ........TerraTec
>     2f 71 61 6e 75 20 55 53 42 32 2e 30 20 48 69 67  /qanu USB2.0 Hig
>   backtrace:
>     [<ffffffff85e169f0>] kmalloc include/linux/slab.h:556 [inline]
>     [<ffffffff85e169f0>] kzalloc include/linux/slab.h:686 [inline]
>     [<ffffffff85e169f0>] cinergyt2_fe_attach+0x40/0x110 drivers/media/usb/dvb-usb/cinergyT2-fe.c:271
>     [<ffffffff85e15b31>] cinergyt2_frontend_attach+0x61/0x140 drivers/media/usb/dvb-usb/cinergyT2-core.c:74 [1]
>     [<ffffffff85dcd71e>] dvb_usb_adapter_frontend_init+0x35e/0x5b0 drivers/media/usb/dvb-usb/dvb-usb-dvb.c:290
>     [<ffffffff88f98e83>] dvb_usb_adapter_init drivers/media/usb/dvb-usb/dvb-usb-init.c:90 [inline]
>     [<ffffffff88f98e83>] dvb_usb_init drivers/media/usb/dvb-usb/dvb-usb-init.c:184 [inline]
> 
> Fixes: 986bd1e58b18 ("V4L/DVB (9107): Alternative version of Terratec Cinergy T2
> driver")
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
> ---
>  drivers/media/usb/dvb-usb/cinergyT2-core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/usb/dvb-usb/cinergyT2-core.c b/drivers/media/usb/dvb-usb/cinergyT2-core.c
> index 969a7ec71dff..fb60af097535 100644
> --- a/drivers/media/usb/dvb-usb/cinergyT2-core.c
> +++ b/drivers/media/usb/dvb-usb/cinergyT2-core.c
> @@ -79,6 +79,7 @@ static int cinergyt2_frontend_attach(struct dvb_usb_adapter *adap)
>  	ret = dvb_usb_generic_rw(d, st->data, 1, st->data, 3, 0);
>  	if (ret < 0) {
>  		deb_rc("cinergyt2_power_ctrl() Failed to retrieve sleep state info\n");
> +		kfree(adap->fe_adap[0].fe);
>  	}
>  	mutex_unlock(&d->data_mutex);
>  
> -- 
> 2.32.0