linux-kernel - Re: [PATCH 1/3] media: mediatek: vcodec: fix h264 multi statless decoder smatch warning

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Message-ID: <9ba79ccf849054974a937d1d605910cf4c8552d6.camel@mediatek.com>
Date: Wed, 3 Apr 2024 03:45:21 +0000
From: Yunfei Dong (董云飞) <Yunfei.Dong@...iatek.com>
To: "nhebert@...omium.org" <nhebert@...omium.org>,
	"benjamin.gaignard@...labora.com" <benjamin.gaignard@...labora.com>,
	"nfraprado@...labora.com" <nfraprado@...labora.com>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>, "nicolas.dufresne@...labora.com"
	<nicolas.dufresne@...labora.com>, "hverkuil-cisco@...all.nl"
	<hverkuil-cisco@...all.nl>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"frkoenig@...omium.org" <frkoenig@...omium.org>, "stevecho@...omium.org"
	<stevecho@...omium.org>, "linux-media@...r.kernel.org"
	<linux-media@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "daniel@...ll.ch" <daniel@...ll.ch>,
	Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>, "hsinyi@...omium.org"
	<hsinyi@...omium.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/3] media: mediatek: vcodec: fix h264 multi statless
 decoder smatch warning

Hi AngeloGioacchino,

Thanks for your reviewing.
On Tue, 2024-04-02 at 11:50 +0200, AngeloGioacchino Del Regno wrote:
> Il 29/02/24 10:56, Yunfei Dong ha scritto:
> > Fix smatch static checker warning for vdec_h264_req_multi_if.c.
> > Leading to kernel crash when fb is NULL.
> > 
> > Fixes: 397edc703a10 ("media: mediatek: vcodec: add h264 decoder")
> > Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
> > ---
> >   .../vcodec/decoder/vdec/vdec_h264_req_multi_if.c         | 9
> > +++++++--
> >   1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git
> > a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
> > _multi_if.c
> > b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
> > _multi_if.c
> > index 0e741e0dc8ba..ab8e708e0df1 100644
> > ---
> > a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
> > _multi_if.c
> > +++
> > b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
> > _multi_if.c
> > @@ -724,11 +724,16 @@ static int vdec_h264_slice_single_decode(void
> > *h_vdec, struct mtk_vcodec_mem *bs
> >   		return vpu_dec_reset(vpu);
> >   
> >   	fb = inst->ctx->dev->vdec_pdata->get_cap_buffer(inst->ctx);
> > +	if (!fb) {
> > +		mtk_vdec_err(inst->ctx, "fb buffer is NULL");
> > +		return -EBUSY;
> > +	}
> > +
> >   	src_buf_info = container_of(bs, struct mtk_video_dec_buf,
> > bs_buffer);
> >   	dst_buf_info = container_of(fb, struct mtk_video_dec_buf,
> > frame_buffer);
> >   
> > -	y_fb_dma = fb ? (u64)fb->base_y.dma_addr : 0;
> > -	c_fb_dma = fb ? (u64)fb->base_c.dma_addr : 0;
> 
> You're changing the behavior here, can you please explain why this
> change is valid
> into the commit description?
> 
The driver already add the condition to check whether fb is NULL at the
front, no need these two lines again.

> Thanks,
> Angelo
> 
Best Regards,
Yunfei Dong
> > +	y_fb_dma = (u64)fb->base_y.dma_addr;
> > +	c_fb_dma = (u64)fb->base_c.dma_addr;
> >   	mtk_vdec_debug(inst->ctx, "[h264-dec] [%d] y_dma=%llx
> > c_dma=%llx",
> >   		       inst->ctx->decoded_frame_cnt, y_fb_dma,
> > c_fb_dma);
> >   
> 
> 
>