linux-kernel - Re: [PATCH v3 03/11] media: videobuf2: Remove VB2_MAX

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Date:   Thu, 22 Jun 2023 16:13:15 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     mchehab@...nel.org, tfiga@...omium.org, m.szyprowski@...sung.com,
        ming.qian@....com, ezequiel@...guardiasur.com.ar,
        p.zabel@...gutronix.de, gregkh@...uxfoundation.org,
        hverkuil-cisco@...all.nl, nicolas.dufresne@...labora.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
        kernel@...labora.com
Subject: Re: [PATCH v3 03/11] media: videobuf2: Remove VB2_MAX_FRAME limit on
 buffer storage


Le 22/06/2023 à 16:11, Dan Carpenter a écrit :
> On Thu, Jun 22, 2023 at 03:13:41PM +0200, Benjamin Gaignard wrote:
>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>> index f1ff7af34a9f..86e1e926fa45 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>> @@ -455,9 +455,9 @@ 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 UINT_MAX */
>>   	num_buffers = min_t(unsigned int, num_buffers,
>> -			    VB2_MAX_FRAME - q->num_buffers);
>> +			    UINT_MAX - q->num_buffers);
>>   
>>   	for (buffer = 0; buffer < num_buffers; ++buffer) {
>>   		/* Allocate vb2 buffer structures */
> Ah...  Here's one of the integer overflow bugs I was talking about.  The
> __vb2_queue_alloc() function returns an int so if num_buffers goes over
> INT_MAX we are hosed.

I will limit it to:
#define VB2_QUEUE_MAX_BUFFERS  (INT_MAX & PAGE_MASK)  /* The mask prevents 85% of integer overflows */
as you have suggest it.

That will be in version 4.

Thanks,
Benjamin

>
> regards,
> dan carpenter
>