Re: [PATCH] media: em28xx: fix memory leak in em28xx_init_dev

From: Dan Carpenter <dan.carpenter@oracle.com>
To: Dongliang Mu <mudongliangabcd@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
	Pavel Skripkin <paskripkin@gmail.com>,
	syzbot <syzkaller@googlegroups.com>,
	linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] media: em28xx: fix memory leak in em28xx_init_dev
Date: Mon, 1 Nov 2021 21:32:50 +0300	[thread overview]
Message-ID: <20211101183249.GA28019@kili> (raw)
In-Reply-To: <20211101095539.423246-1-mudongliangabcd@gmail.com>

On Mon, Nov 01, 2021 at 05:55:39PM +0800, Dongliang Mu wrote:
> In the em28xx_init_rev, if em28xx_audio_setup fails, this function fails
> to deallocate the media_dev allocated in the em28xx_media_device_init.
> 
> Fix this by adding em28xx_unregister_media_device to free media_dev.
> 
> BTW, this patch is tested in my local syzkaller instance, and it can
> prevent the memory leak from occurring again.
> 
> CC: Pavel Skripkin <paskripkin@gmail.com>
> Fixes: 37ecc7b1278f ("[media] em28xx: add media controller support")
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>

Is this really a syzbot warning?  If so it should be in the format:

Reported-by: syzbot+4c4ffd1e1094dae61035@syzkaller.appspotmail.com

Syzbot is different from syzkaller.  Syzkaller is the fuzzer and syzbot
is the program which reports syzkaller bugs.

> ---
>  drivers/media/usb/em28xx/em28xx-cards.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index c1e0dccb7408..fca68939ca50 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -3625,8 +3625,10 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
>  

There is no check to see if the em28xx_media_device_init() fails.  I
don't love that we call unregister() to undo the init() but it seems
like it should work...

>  	if (dev->is_audio_only) {
>  		retval = em28xx_audio_setup(dev);
> -		if (retval)
> -			return -ENODEV;
> +		if (retval) {
> +			retval = -ENODEV;

This was in the original code, but probably we should preserve the
error code.

> +			goto err_deinit_media;
> +		}

regards,
dan carpenter