linux-kernel - Re: [PATCH v2 02/10] EDAC/mc: Use int type for parameters of edac_mc

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Message-ID: <20200519093324.33pamvpzhxuzg7a2@rric.localdomain>
Date:   Tue, 19 May 2020 11:33:24 +0200
From:   Robert Richter <rrichter@...vell.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Aristeu Rozanski <aris@...hat.com>,
        Matthias Brugger <mbrugger@...e.com>,
        <linux-edac@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 02/10] EDAC/mc: Use int type for parameters of
 edac_mc_alloc()

On 23.04.20 19:49:34, Borislav Petkov wrote:
> On Wed, Apr 22, 2020 at 01:58:06PM +0200, Robert Richter wrote:
> > Most iterators use int type as index. mci->mc_idx is also type int. So
> > use int type for parameters of edac_mc_alloc(). Extend the range check
> > to check for negative values. There is a type cast now when assigning
> > variable n_layers to mci->n_layer, it is safe due to the range check.
> > 
> > While at it, rename the users of edac_mc_alloc() to mc_idx as this
> > fits better here.
> > 
> > Signed-off-by: Robert Richter <rrichter@...vell.com>
> > ---
> >  drivers/edac/edac_mc.c | 7 +++----
> >  drivers/edac/edac_mc.h | 6 +++---
> >  2 files changed, 6 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> > index 107d7c4de933..57d1d356d69c 100644
> > --- a/drivers/edac/edac_mc.c
> > +++ b/drivers/edac/edac_mc.c
> > @@ -444,8 +444,7 @@ static int edac_mc_alloc_dimms(struct mem_ctl_info *mci)
> >  	return 0;
> >  }
> >  
> > -struct mem_ctl_info *edac_mc_alloc(unsigned int mc_num,
> > -				   unsigned int n_layers,
> > +struct mem_ctl_info *edac_mc_alloc(int mc_idx, int n_layers,
> >  				   struct edac_mc_layer *layers,
> >  				   unsigned int sz_pvt)
> >  {
> > @@ -456,7 +455,7 @@ struct mem_ctl_info *edac_mc_alloc(unsigned int mc_num,
> >  	void *pvt, *ptr = NULL;
> >  	bool per_rank = false;
> >  
> > -	if (WARN_ON(n_layers > EDAC_MAX_LAYERS || n_layers == 0))
> > +	if (WARN_ON(mc_idx < 0 || n_layers < 1 || n_layers > EDAC_MAX_LAYERS))
> >  		return NULL;
> 
> Yeah, no, this doesn't make sense to me. The memory controller number
> and the number of layers can never ever be negative and thus signed.
> 
> And some drivers supply unsigned types and some signed. So if anything,
> this should be fixing all the callers to supply unsigned quantities.

mci->mc_idx is of type int and there is a cast here that should be
fixed. IMO that should be a signed int as some interfaces (esp. if you
search for an index) that require a negative value to report errors or
something could not be found.

So let's take this patch out of this series if you want have it
different.

Thanks,

-Robert