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

[Hangyu Hua]

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@xxxxxxxxx>
> > ---
> >   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,