All of lore.kernel.org
 help / color / mirror / Atom feed
From: Hans Verkuil <hverkuil@xs4all.nl>
To: Pavel Skripkin <paskripkin@gmail.com>
Cc: mchehab@kernel.org, linux-media@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com
Subject: Re: [PATCH] media: em28xx: fix corrupted list
Date: Wed, 21 Jul 2021 14:25:34 +0200	[thread overview]
Message-ID: <7df1705e-b2c7-ddfc-9cc5-582fb1a304e5@xs4all.nl> (raw)
In-Reply-To: <20210721152154.6b1a4e68@gmail.com>

On 21/07/2021 14:21, Pavel Skripkin wrote:
> On Tue, 20 Jul 2021 14:13:13 +0200
> Hans Verkuil <hverkuil@xs4all.nl> wrote:
> 
>> On 06/07/2021 16:50, Pavel Skripkin wrote:
>>> Syzbot reported corrupted list in em28xx driver. The problem was in
>>> non-reinitialized lists on disconnect. Since all 2 lists are global
>>> variables and driver can be connected and disconnected many times we
>>> should call INIT_LIST_HEAD() in .disconnect method to prevent
>>> corrupted list entries.
>>>
>>> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code
>>> to a proper place") Reported-by:
>>> syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com
>>> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> ---
>>>  drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
>>>  drivers/media/usb/em28xx/em28xx-core.c  | 6 ++++++
>>>  drivers/media/usb/em28xx/em28xx.h       | 1 +
>>>  3 files changed, 9 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c
>>> b/drivers/media/usb/em28xx/em28xx-cards.c index
>>> ba9292e2a587..8b1ff79c37a0 100644 ---
>>> a/drivers/media/usb/em28xx/em28xx-cards.c +++
>>> b/drivers/media/usb/em28xx/em28xx-cards.c @@ -4148,6 +4148,8 @@
>>> static void em28xx_usb_disconnect(struct usb_interface *intf)
>>> dev->dev_next = NULL; }
>>>  	kref_put(&dev->ref, em28xx_free_device);
>>> +
>>> +	em28xx_reset_lists();
>>>  }
>>>  
>>>  static int em28xx_usb_suspend(struct usb_interface *intf,
>>> diff --git a/drivers/media/usb/em28xx/em28xx-core.c
>>> b/drivers/media/usb/em28xx/em28xx-core.c index
>>> 584fa400cd7d..03970ed00dba 100644 ---
>>> a/drivers/media/usb/em28xx/em28xx-core.c +++
>>> b/drivers/media/usb/em28xx/em28xx-core.c @@ -1131,6 +1131,12 @@
>>> void em28xx_init_extension(struct em28xx *dev)
>>> mutex_unlock(&em28xx_devlist_mutex); }
>>>  
>>> +void em28xx_reset_lists(void)
>>> +{
>>> +	INIT_LIST_HEAD(&em28xx_devlist);
>>> +	INIT_LIST_HEAD(&em28xx_extension_devlist);
>>
>> This needs a mutex_lock(&em28xx_devlist_mutex);
>>
>> But actually, I don't think this is right: if there are multiple
>> em28xx devices, then I think if you disconnect one, then the other is
>> - with this code - also removed from the list.
>>
>> Can you give a link to the actual syzbot bug? I'm not at all sure you
>> are fixing the right thing here.
> 
> Hi, Hans!
> 
> I guess, I missed my coffee that morning, sorry :) This patch looks
> complety wrong, of course.
> 
> I've took a close look at this bug one more time, and I found the true
> root case of this bug.
> 
> If em28xx dev has dev_next pointer we need to close dev->next extension
> on disconnect to avoid UAF and corrupted list bug. So, something like
> this should work:
> 
> 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);
> +	}
>  	em28xx_release_resources(dev);
>  
>  	if (dev->dev_next) {
> 
> How to You feel about it? I am going to send this patch for syzbot
> testing

That looks a lot saner :-)

> 
> 
> Syzbot link:
> https://syzkaller.appspot.com/bug?id=3609bbf45bf63a8f6032f330eb3d34f51cc81493
> 
> 
> Again, sorry for v1 patch, I don't know how I came up with this fix :(

No problem, just post a v2 if syzbot passes.

Regards,

	Hans

>  
> 
> 
> With regards,
> Pavel Skripkin
> 


  reply	other threads:[~2021-07-21 12:25 UTC|newest]

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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=7df1705e-b2c7-ddfc-9cc5-582fb1a304e5@xs4all.nl \
    --to=hverkuil@xs4all.nl \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=mchehab@kernel.org \
    --cc=paskripkin@gmail.com \
    --cc=syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com \
    --subject='Re: [PATCH] media: em28xx: fix corrupted list' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.