From: Hans Verkuil <hverkuil@xs4all.nl>
To: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>,
linux-media@vger.kernel.org
Cc: dafna3@gmail.com, helen.koike@collabora.com,
ezequiel@collabora.com, stable@vger.kernel.org
Subject: Re: [PATCH v3] media: v4l2-core: fix a use-after-free bug of sd->devnode
Date: Fri, 17 Jan 2020 11:46:42 +0100 [thread overview]
Message-ID: <2cf9c519-14d8-1a1d-d1b8-aea428deee5a@xs4all.nl> (raw)
In-Reply-To: <d0505bd7-920e-d0f2-3aa2-440f27e7c08f@collabora.com>
On 1/17/20 11:35 AM, Dafna Hirschfeld wrote:
> Hi
>
> On 16.01.20 13:57, Hans Verkuil wrote:
>> On 11/20/19 1:22 PM, Dafna Hirschfeld wrote:
>>> sd->devnode is released after calling
>>> v4l2_subdev_release. Therefore it should be set
>>> to NULL so that the subdev won't hold a pointer
>>> to a released object. This fixes a reference
>>> after free bug in function
>>> v4l2_device_unregister_subdev
>>>
>>> Cc: stable@vger.kernel.org
>>> Fixes: 0e43734d4c46e ("media: v4l2-subdev: add release() internal op")
>>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
>>> Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
>>> ---
>>> changes since v2:
>>> - since this is a regresion fix, I added Fixes and Cc to stable tags,
>>> - change the commit title and log to be more clear.
>>>
>>> drivers/media/v4l2-core/v4l2-device.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
>>> index 63d6b147b21e..2b3595671d62 100644
>>> --- a/drivers/media/v4l2-core/v4l2-device.c
>>> +++ b/drivers/media/v4l2-core/v4l2-device.c
>>> @@ -177,6 +177,7 @@ static void v4l2_subdev_release(struct v4l2_subdev *sd)
>>> {
>>> struct module *owner = !sd->owner_v4l2_dev ? sd->owner : NULL;
>>>
>>> + sd->devnode = NULL;
>>> if (sd->internal_ops && sd->internal_ops->release)
>>> sd->internal_ops->release(sd);
>>
>> I'd move the sd->devnode = NULL; line here. That way the
>> sd->internal_ops->release(sd) callback can still use it.
>>
>> Unless I am missing something?
> It makes sense although none of the drivers uses this callback since
> the subdevice should be released in the v4l2_device's release so it
> seems that this callback can (should?) be removed.
If nobody uses it, then I agree that it is better to remove it.
Regards,
Hans
>
> Dafna
>
>>
>>> module_put(owner);
>>>
>>
>> Regards,
>>
>> Hans
>>
next prev parent reply other threads:[~2020-01-17 10:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 12:22 [PATCH v3] media: v4l2-core: fix a use-after-free bug of sd->devnode Dafna Hirschfeld
2020-01-16 11:57 ` Hans Verkuil
2020-01-17 10:35 ` Dafna Hirschfeld
2020-01-17 10:46 ` Hans Verkuil [this message]
2020-01-17 10:52 ` Dafna Hirschfeld
2020-01-31 15:42 ` Ezequiel Garcia
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