netdev - Re: [PATCH net-next v4 01/10] net: sunhme: Fix uninitialized return code

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Date:   Sat, 25 Mar 2023 09:26:31 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Sean Anderson <seanga2@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>
Subject: Re: [PATCH net-next v4 01/10] net: sunhme: Fix uninitialized return
 code

On Sat, Mar 25, 2023 at 09:17:03AM +0100, Simon Horman wrote:
> Hi Sean,
> 
> On Fri, Mar 24, 2023 at 01:51:27PM -0400, Sean Anderson wrote:
> > Fix an uninitialized return code if we never found a qfe slot. It would be
> > a bug if we ever got into this situation, but it's good to return something
> > tracable.
> > 
> > Fixes: acb3f35f920b ("sunhme: forward the error code from pci_enable_device()")
> 
> I think it might be,
> 
> Fixes: 5b3dc6dda6b1 ("sunhme: Regularize probe errors")
> 
> > Reported-by: kernel test robot <lkp@...el.com>
> > Reported-by: Dan Carpenter <error27@...il.com>
> 
> Checkpatch requests a Link tag after Reported-by tags.
> 
> Link: https://lore.kernel.org/oe-kbuild/20230222135715.hjXBN9H5dr7nCnI_Ye2s5H--HsnWom4o9AMScThhDRM@z/T/
> 
> > Signed-off-by: Sean Anderson <seanga2@...il.com>
> > ---
> > 
> > Changes in v4:
> > - Move this fix to its own commit
> > 
> >  drivers/net/ethernet/sun/sunhme.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/sun/sunhme.c b/drivers/net/ethernet/sun/sunhme.c
> > index b0c7ab74a82e..7cf8210ebbec 100644
> > --- a/drivers/net/ethernet/sun/sunhme.c
> > +++ b/drivers/net/ethernet/sun/sunhme.c
> > @@ -2834,7 +2834,7 @@ static int happy_meal_pci_probe(struct pci_dev *pdev,
> >  	int i, qfe_slot = -1;
> >  	char prom_name[64];
> >  	u8 addr[ETH_ALEN];
> > -	int err;
> > +	int err = -ENODEV;
> >  
> >  	/* Now make sure pci_dev cookie is there. */
> >  #ifdef CONFIG_SPARC
> 
> Unfortunately I don't think this is the right fix,
> and indeed smatch still complains with it applied.
> 
> The reason is that a few lines further down there is:
> 
>         err = pcim_enable_device(pdev);
>         if (err)
>                 goto err_out;
> 
> Which overrides the initialisation of err.
> Before getting to the line that smatch highlights, correctly as far
> as I can tell, as having a missing error code.
> 
> 			if (qfe_slot == 4)
> 				goto err_out;
> 
> As err_out simply calls 'return err' one could just return here.
> And perhaps that is a nice cleanup to roll out at some point.

I see that point is patch 9/10, which also fixes the bug
reported by smatch :)

> But to be in keeping with the style of the function, as a minimal fix,
> I think the following might be appropriate.
> 
> Note, with this applied err doesn't need to be initialised at the top of
> the function (as far as my invocation of smatch is concerned).
> 
> diff --git a/drivers/net/ethernet/sun/sunhme.c b/drivers/net/ethernet/sun/sunhme.c
> index b0c7ab74a82e..d6df778a0052 100644
> --- a/drivers/net/ethernet/sun/sunhme.c
> +++ b/drivers/net/ethernet/sun/sunhme.c
> @@ -2863,8 +2863,10 @@ static int happy_meal_pci_probe(struct pci_dev *pdev,
>  			if (!qp->happy_meals[qfe_slot])
>  				break;
>  
> -		if (qfe_slot == 4)
> +		if (qfe_slot == 4) {
> +			err = -ENODEV;
>  			goto err_out;
> +		}
>  	}
>  
>  	dev = devm_alloc_etherdev(&pdev->dev, sizeof(struct happy_meal));
>