linux-kernel - Re: [PATCH 2/5] drm/mediatek: Add cnt checking for coverity issue

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Message-ID: <1e4a70709ad588feb85c9cd0d1bbc0a2f78e525d.camel@mediatek.com>
Date:   Tue, 13 Jun 2023 07:07:38 +0000
From:   Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>
To:     CK Hu (胡俊光) <ck.hu@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        Jason-ch Chen (陳建豪) 
        <Jason-ch.Chen@...iatek.com>,
        Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        Rex-BC Chen (陳柏辰) 
        <Rex-BC.Chen@...iatek.com>
Subject: Re: [PATCH 2/5] drm/mediatek: Add cnt checking for coverity issue

Hi CK,

Thanks for the reviews.

On Mon, 2023-06-12 at 08:21 +0000, CK Hu (胡俊光) wrote:
> Hi, Jason:
> 
> On Fri, 2023-04-07 at 14:46 +0800, Jason-JH.Lin wrote:
> > CERT-C Characters and Strings (CERT STR31-C)
> > all_drm_priv[cnt] evaluates to an address that could be at negative
> > offset of an array.
> > 
> > In mtk_drm_get_all_drm_priv():
> > Guarantee that storage for strings has sufficient space for
> > character
> > data and the null terminator.
> > 
> > So change cnt to unsigned int and check its max value.
> > 
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> > Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195
> > multi mmsys support")
> > ---
> >  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > index 86255a066faf..fcfa10332166 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > @@ -378,7 +378,7 @@ static bool mtk_drm_get_all_drm_priv(struct
> > device *dev)
> >  	const struct of_device_id *of_id;
> >  	struct device_node *node;
> >  	struct device *drm_dev;
> > -	int cnt = 0;
> > +	unsigned int cnt = 0;
> >  	int i, j;
> >  
> >  	for_each_child_of_node(phandle->parent, node) {
> > @@ -397,7 +397,7 @@ static bool mtk_drm_get_all_drm_priv(struct
> > device *dev)
> >  			continue;
> >  
> >  		all_drm_priv[cnt] = dev_get_drvdata(drm_dev);
> > -		if (all_drm_priv[cnt] && all_drm_priv[cnt]-
> > > mtk_drm_bound)
> > 
> > +		if (cnt < MAX_CRTC && all_drm_priv[cnt] &&
> > all_drm_priv[cnt]->mtk_drm_bound)
> >  			cnt++;
> 
> 
> I would like to add below statement here:
> 
> 		if (cnt == MAX_CRTC)
> 			break;
> 
> Regards,
> CK

OK, I'll change to this statement.


Regards,
Jason-JH.Lin
> 
> >  	}
> >