linux-kernel - Re: [PATCH] media: dvb_vb2: fix possible out of bound access

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Date:   Thu, 19 May 2022 09:44:25 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>, mchehab@...nel.org,
        senozhatsky@...omium.org, caihuoqing@...du.com
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: dvb_vb2: fix possible out of bound access

On 2022/5/18 18:44, Hans Verkuil wrote:
> Hi Hangyu,
> 
> It appears this patch fell through the cracks. It's certainly useful to
> have.
> 
> On 3/24/22 09:01, Hangyu Hua wrote:
>> vb2_core_qbuf and vb2_core_querybuf don't check the range of b->index
>> controlled by the user.
>>
>> Fix this by adding range checking code before using them.
>>
>> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
>> ---
>>   drivers/media/dvb-core/dvb_vb2.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/media/dvb-core/dvb_vb2.c b/drivers/media/dvb-core/dvb_vb2.c
>> index a1bd6d9c9223..f410800b92e7 100644
>> --- a/drivers/media/dvb-core/dvb_vb2.c
>> +++ b/drivers/media/dvb-core/dvb_vb2.c
>> @@ -354,6 +354,12 @@ int dvb_vb2_reqbufs(struct dvb_vb2_ctx *ctx, struct dmx_requestbuffers *req)
>>   
>>   int dvb_vb2_querybuf(struct dvb_vb2_ctx *ctx, struct dmx_buffer *b)
>>   {
>> +	struct vb2_queue *q = &ctx->vb_q;
>> +
>> +	if (b->index >= q->num_buffers) {
>> +		dprintk(q, 1, "buffer index out of range\n");
> 
> However, this patch doesn't compile: dprintk in this source doesn't
> have a 'q' argument!

Oops, i will fix this out.

> 
>> +		return -EINVAL;
>> +	}
>>   	vb2_core_querybuf(&ctx->vb_q, b->index, b);
>>   	dprintk(3, "[%s] index=%d\n", ctx->name, b->index);
> 
> Also, to help debugging it prefixes the warnings with the ctx-name.
> 
> Can you post a v2 of this patch?
> 
> Regards,
> 
> 	Hans

I will send a v2 later.

Thanks,
Hangyu

> 
>>   	return 0;
>> @@ -378,8 +384,13 @@ int dvb_vb2_expbuf(struct dvb_vb2_ctx *ctx, struct dmx_exportbuffer *exp)
>>   
>>   int dvb_vb2_qbuf(struct dvb_vb2_ctx *ctx, struct dmx_buffer *b)
>>   {
>> +	struct vb2_queue *q = &ctx->vb_q;
>>   	int ret;
>>   
>> +	if (b->index >= q->num_buffers) {
>> +		dprintk(q, 1, "buffer index out of range\n");
>> +		return -EINVAL;
>> +	}
>>   	ret = vb2_core_qbuf(&ctx->vb_q, b->index, b, NULL);
>>   	if (ret) {
>>   		dprintk(1, "[%s] index=%d errno=%d\n", ctx->name,