netdev - Re: [PATCH net] Octeontx2-af: Fix negative array index read warning

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Message-ID: <CADBJw5aqQCprGJvG2T4v2_O6BK2dh+2cZRLbyryyktucsqHtVg@mail.gmail.com>
Date: Wed, 13 Aug 2025 00:31:22 +0530
From: Chandra Mohan Sundar <chandramohan.explore@...il.com>
To: Joe Damato <joe@...a.to>, Chandra Mohan Sundar <chandramohan.explore@...il.com>, sgoutham@...vell.com, 
	lcherian@...vell.com, gakula@...vell.com, jerinj@...vell.com, 
	hkelam@...vell.com, sbhatta@...vell.com, andrew+netdev@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	shuah@...nel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH net] Octeontx2-af: Fix negative array index read warning

On Mon, 11 Aug 2025 16:37:14 -0700, Joe Damato wrote:
>A couple pieces of feedback for you:

>1. Since this is a fixes it needs a Fixes tag and a commit SHA that it is fixing.

Thank you very much for your feedback.I will add the Fixes tag as suggested.

>2. cgx_get_cgxid is called in 3 places, so your patch would probably need to
>   be expanded to fix all uses?

Thanks for the suggestion.
I can add a similar check in cgxlmac_to_pf() to check if cgx_id is
negative and return an error.

>Overall though, did you somehow trigger this issue?
>
>It seems like all cases where cgx_get_cgxid is used it would be extremely
>difficult (maybe impossible?) for cgxd to be NULL and for it to return a
>negative value.

I could not reproduce a scenario where cgx_get_cgxid returns a
negative value. However, this issue was reported by the Black Duck
Coverity scan.
The fix was made to cover all possible return paths.

Please advise if you think there’s a better way to address it.

Thanks,
Chandra Mohan Sundar


On Tue, Aug 12, 2025 at 5:07 AM Joe Damato <joe@...a.to> wrote:
>
> On Sun, Aug 10, 2025 at 11:33:27PM +0530, Chandra Mohan Sundar wrote:
> > The cgx_get_cgxid function may return a negative value.
> > Using this value directly as an array index triggers Coverity warnings.
> >
> > Validate the returned value and handle the case gracefully.
> >
> > Signed-off-by: Chandra Mohan Sundar <chandramohan.explore@...il.com>
> > ---
> >  drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
> > index 8375f18c8e07..b14de93a2481 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_debugfs.c
> > @@ -3005,6 +3005,8 @@ static int cgx_print_fwdata(struct seq_file *s, int lmac_id)
> >               return -EAGAIN;
> >
> >       cgx_id = cgx_get_cgxid(cgxd);
> > +     if (cgx_id < 0)
> > +             return -EINVAL;
> >
> >       if (rvu->hw->lmac_per_cgx == CGX_LMACS_USX)
> >               fwdata =  &rvu->fwdata->cgx_fw_data_usx[cgx_id][lmac_id];
>
> A couple pieces of feedback for you:
>
> 1. Since this is a fixes it needs a Fixes tag and a commit SHA that it is fixing.
> 2. cgx_get_cgxid is called in 3 places, so your patch would probably need to
>    be expanded to fix all uses?
>
> Overall though, did you somehow trigger this issue?
>
> It seems like all cases where cgx_get_cgxid is used it would be extremely
> difficult (maybe impossible?) for cgxd to be NULL and for it to return a
> negative value.