From: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
To: Hans Verkuil <hverkuil@xs4all.nl>, 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 12:35:20 +0200 [thread overview]
Message-ID: <d0505bd7-920e-d0f2-3aa2-440f27e7c08f@collabora.com> (raw)
In-Reply-To: <fe36e4a9-2369-3150-b823-97fb4bf1afe4@xs4all.nl>
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.
Dafna
>
>> module_put(owner);
>>
>
> Regards,
>
> Hans
>
next prev parent reply other threads:[~2020-01-17 10:35 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 [this message]
2020-01-17 10:46 ` Hans Verkuil
2020-01-17 10:52 ` Dafna Hirschfeld
2020-01-31 15:42 ` Ezequiel Garcia
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