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From: Hans Verkuil <hverkuil@xs4all.nl>
To: Pavel Skripkin <paskripkin@gmail.com>, mchehab@kernel.org
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com
Subject: Re: [PATCH v2] media: em28xx: add missing em28xx_close_extension
Date: Thu, 29 Jul 2021 11:45:19 +0200	[thread overview]
Message-ID: <3b1de658-ebf0-e45f-49ef-953e3467e7d4@xs4all.nl> (raw)
In-Reply-To: <20210721194307.12155-1-paskripkin@gmail.com>

On 21/07/2021 21:43, Pavel Skripkin wrote:
> If em28xx dev has ->dev_next pointer, we need to delete dev_next list node
> from em28xx_extension_devlist on disconnect to avoid UAF bugs and
> corrupted list bugs, since driver frees this pointer on disconnect.
> 
> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
> Reported-and-tested-by: syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
> 
> Changes in v2:
> 	Previous patch was completely broken. I've done some debugging
> 	again and found true root case of the reported bug.
> 
> ---
>  drivers/media/usb/em28xx/em28xx-cards.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index c1e0dccb7408..d56b040e1bd7 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
>  
>  	em28xx_close_extension(dev);
>  
> -	if (dev->dev_next)
> +	if (dev->dev_next) {
>  		em28xx_release_resources(dev->dev_next);
> +		em28xx_close_extension(dev->dev_next);

Wouldn't it be better to swap these two?

That order is also used for em28xx_close_extension(dev) and em28xx_release_resources(dev).

You do need to store dev->dev_next in a temp variable, though.

Regards,

	Hans

> +	}
>  	em28xx_release_resources(dev);
>  
>  	if (dev->dev_next) {
> 


  reply	other threads:[~2021-07-29  9:45 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-06 14:50 [PATCH] media: em28xx: fix corrupted list Pavel Skripkin
2021-07-20 12:13 ` Hans Verkuil
2021-07-21 12:21   ` Pavel Skripkin
2021-07-21 12:25     ` Hans Verkuil
2021-07-21 19:43       ` [PATCH v2] media: em28xx: add missing em28xx_close_extension Pavel Skripkin
2021-07-29  9:45         ` Hans Verkuil [this message]
2021-07-29 12:45           ` Pavel Skripkin
2021-07-29 13:40             ` Hans Verkuil
2021-07-29 20:23               ` [PATCH v3] " Pavel Skripkin

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