linux-kernel - Re: [PATCH v2] media: videobuf2: forbid remove

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Message-ID: <9df0295d-418b-46ea-958a-a025de8b62e7@kernel.org>
Date: Thu, 23 Oct 2025 11:01:18 +0200
From: Hans Verkuil <hverkuil+cisco@...nel.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Tomasz Figa <tfiga@...omium.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Guennadi Liakhovetski <g.liakhovetski@....de>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Hans Verkuil <hverkuil@...nel.org>, stable@...r.kernel.org,
 Shuangpeng Bai <SJB7183@....edu>
Subject: Re: [PATCH v2] media: videobuf2: forbid remove_bufs when legacy
 fileio is active

On 21/10/2025 11:56, Hans Verkuil wrote:
> Hi Marek,
> 
> On 20/10/2025 18:01, Marek Szyprowski wrote:
>> vb2_ioctl_remove_bufs() call manipulates queue internal buffer list,
>> potentially overwriting some pointers used by the legacy fileio access
>> mode. Add a vb2_verify_memory_type() check symmetrical to
>> vb2_ioctl_create_bufs() to forbid that ioctl when fileio is active to
>> protect internal queue state between subsequent read/write calls.
>>
>> CC: stable@...r.kernel.org
>> Fixes: a3293a85381e ("media: v4l2: Add REMOVE_BUFS ioctl")
>> Reported-by: Shuangpeng Bai<SJB7183@....edu>
>> Suggested-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> 
> I'll pick this up as a fix for v6.18. I think this is important enough to
> not wait for v6.19.

Hmm, it's failing on v4l2-compliance. I'm debugging to see whether it is a
kernel or v4l2-compliance problem.

Regards,

	Hans

> 
> Regards,
> 
> 	Hans
> 
>> ---
>> v2:
>> - dropped a change to vb2_ioctl_create_bufs(), as it is already handled
>>   by the vb2_verify_memory_type() call
>> - replaced queue->type check in vb2_ioctl_remove_bufs() by a call to
>>   vb2_verify_memory_type() which covers all cases
>>
>> v1: https://lore.kernel.org/all/20251016111154.993949-1-m.szyprowski@samsung.com/
>> ---
>>  drivers/media/common/videobuf2/videobuf2-v4l2.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> index d911021c1bb0..0de7490292fe 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> @@ -1000,9 +1000,11 @@ int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>>  			  struct v4l2_remove_buffers *d)
>>  {
>>  	struct video_device *vdev = video_devdata(file);
>> +	int res;
>>  
>> -	if (vdev->queue->type != d->type)
>> -		return -EINVAL;
>> +	res = vb2_verify_memory_type(vdev->queue, vdev->queue->memory, d->type);
>> +	if (res)
>> +		return res;
>>  
>>  	if (d->count == 0)
>>  		return 0;
> 
>