Re: [PATCH v6 11/18] media: videobuf2: Be more flexible on the number of queue stored buffers

[Benjamin Gaignard <benjamin.gaignard@collabora.com>]

Le 04/09/2023 à 13:24, Hans Verkuil a écrit :
> Hi Benjamin,
>
> On 01/09/2023 14:44, Benjamin Gaignard wrote:
>> Add 'max_allowed_buffers' field in vb2_queue struct to let drivers decide
>> how many buffers could be stored in a queue.
>> This request 'bufs' array to be allocated at queue init time and freed
>> when releasing the queue.
>> By default VB2_MAX_FRAME remains the limit.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> ---
>>   .../media/common/videobuf2/videobuf2-core.c   | 25 +++++++++++++------
>>   include/media/videobuf2-core.h                |  4 ++-
>>   2 files changed, 20 insertions(+), 9 deletions(-)
>>
> This patch breaks v4l2-compliance. I see lots of issues when running the
> test-media script in v4l-utils, contrib/test, among them memory leaks
> and use-after-free.
>
> I actually tested using virtme with the build scripts, but that in turn
> calls the test-media script in a qemu environment, and it is at the moment
> a bit tricky to set up, unless you run a debian 12 distro.
>
> I will email the test logs directly to you since they are a bit large (>5000 lines).

I will try to reproduce this error on my side to fix it.

Regards,
Benjamin

>
> Regards,
>
> 	Hans
>
>
>
>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>> index 15b583ce0c69..dc7f6b59d237 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>> @@ -411,7 +411,7 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
>>    */
>>   static bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
>>   {
>> -	if (index < VB2_MAX_FRAME && !q->bufs[index]) {
>> +	if (index < q->max_allowed_buffers && !q->bufs[index]) {
>>   		q->bufs[index] = vb;
>>   		vb->index = index;
>>   		vb->vb2_queue = q;
>> @@ -428,7 +428,7 @@ static bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, uns
>>    */
>>   static void vb2_queue_remove_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>>   {
>> -	if (vb->index < VB2_MAX_FRAME) {
>> +	if (vb->index < q->max_allowed_buffers) {
>>   		q->bufs[vb->index] = NULL;
>>   		vb->vb2_queue = NULL;
>>   	}
>> @@ -449,9 +449,9 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>   	struct vb2_buffer *vb;
>>   	int ret;
>>   
>> -	/* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */
>> +	/* Ensure that q->num_buffers+num_buffers is below q->max_allowed_buffers */
>>   	num_buffers = min_t(unsigned int, num_buffers,
>> -			    VB2_MAX_FRAME - q->num_buffers);
>> +			    q->max_allowed_buffers - q->num_buffers);
>>   
>>   	for (buffer = 0; buffer < num_buffers; ++buffer) {
>>   		/* Allocate vb2 buffer structures */
>> @@ -862,9 +862,9 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>>   	/*
>>   	 * Make sure the requested values and current defaults are sane.
>>   	 */
>> -	WARN_ON(q->min_buffers_needed > VB2_MAX_FRAME);
>> +	WARN_ON(q->min_buffers_needed > q->max_allowed_buffers);
>>   	num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
>> -	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
>> +	num_buffers = min_t(unsigned int, num_buffers, q->max_allowed_buffers);
>>   	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
>>   	/*
>>   	 * Set this now to ensure that drivers see the correct q->memory value
>> @@ -980,7 +980,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>   	bool no_previous_buffers = !q->num_buffers;
>>   	int ret;
>>   
>> -	if (q->num_buffers == VB2_MAX_FRAME) {
>> +	if (q->num_buffers == q->max_allowed_buffers) {
>>   		dprintk(q, 1, "maximum number of buffers already allocated\n");
>>   		return -ENOBUFS;
>>   	}
>> @@ -1009,7 +1009,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>   			return -EINVAL;
>>   	}
>>   
>> -	num_buffers = min(*count, VB2_MAX_FRAME - q->num_buffers);
>> +	num_buffers = min(*count, q->max_allowed_buffers - q->num_buffers);
>>   
>>   	if (requested_planes && requested_sizes) {
>>   		num_planes = requested_planes;
>> @@ -2519,6 +2519,14 @@ int vb2_core_queue_init(struct vb2_queue *q)
>>   
>>   	q->memory = VB2_MEMORY_UNKNOWN;
>>   
>> +	if (!q->max_allowed_buffers)
>> +		q->max_allowed_buffers = VB2_MAX_FRAME;
>> +
>> +	/* The maximum is limited by offset cookie encoding pattern */
>> +	q->max_allowed_buffers = min_t(unsigned int, q->max_allowed_buffers, BUFFER_INDEX_MASK);
>> +
>> +	q->bufs = kcalloc(q->max_allowed_buffers, sizeof(*q->bufs), GFP_KERNEL);
>> +
>>   	if (q->buf_struct_size == 0)
>>   		q->buf_struct_size = sizeof(struct vb2_buffer);
>>   
>> @@ -2543,6 +2551,7 @@ void vb2_core_queue_release(struct vb2_queue *q)
>>   	__vb2_queue_cancel(q);
>>   	mutex_lock(&q->mmap_lock);
>>   	__vb2_queue_free(q, q->num_buffers);
>> +	kfree(q->bufs);
>>   	mutex_unlock(&q->mmap_lock);
>>   }
>>   EXPORT_SYMBOL_GPL(vb2_core_queue_release);
>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>> index cd3ff1cd759d..97153c69583f 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>> @@ -558,6 +558,7 @@ struct vb2_buf_ops {
>>    * @dma_dir:	DMA mapping direction.
>>    * @bufs:	videobuf2 buffer structures
>>    * @num_buffers: number of allocated/used buffers
>> + * @max_allowed_buffers: upper limit of number of allocated/used buffers
>>    * @queued_list: list of buffers currently queued from userspace
>>    * @queued_count: number of buffers queued and ready for streaming.
>>    * @owned_by_drv_count: number of buffers owned by the driver
>> @@ -619,8 +620,9 @@ struct vb2_queue {
>>   	struct mutex			mmap_lock;
>>   	unsigned int			memory;
>>   	enum dma_data_direction		dma_dir;
>> -	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
>> +	struct vb2_buffer		**bufs;
>>   	unsigned int			num_buffers;
>> +	unsigned int			max_allowed_buffers;
>>   
>>   	struct list_head		queued_list;
>>   	unsigned int			queued_count;
>