linux-kernel - Re: [PATCH v2] mtd: rawnand: mark expected switch fall-throughs

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Message-ID: <20190412092419.6f5a6432@xps13>
Date:   Fri, 12 Apr 2019 09:24:19 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Kyungmin Park <kyungmin.park@...sung.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Wan ZongShun <mcuos.com@...il.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2] mtd: rawnand: mark expected switch fall-throughs

Hi Gustavo,

"Gustavo A. R. Silva" <gustavo@...eddedor.com> wrote on Thu, 11 Apr
2019 17:20:31 -0500:

> On 4/11/19 5:10 PM, Miquel Raynal wrote:
> > Hi Gustavo,
> > 
> > "Gustavo A. R. Silva" <gustavo@...eddedor.com> wrote on Thu, 11 Apr
> > 2019 13:30:31 -0500:
> >   
> >> Hi Miquel,
> >>
> >> On 2/5/19 6:55 AM, Miquel Raynal wrote:
> >> [..]  
> >>>> @@ -3280,12 +3280,14 @@ static void onenand_check_features(struct mtd_info *mtd)
> >>>>  			if ((this->version_id & 0xf) == 0xe)
> >>>>  				this->options |= ONENAND_HAS_NOP_1;
> >>>>  		}
> >>>> +		/* fall through */
> >>>>  
> >>>>  	case ONENAND_DEVICE_DENSITY_2Gb:
> >>>>  		/* 2Gb DDP does not have 2 plane */
> >>>>  		if (!ONENAND_IS_DDP(this))
> >>>>  			this->options |= ONENAND_HAS_2PLANE;
> >>>>  		this->options |= ONENAND_HAS_UNLOCK_ALL;
> >>>> +		/* fall through */    
> >>>
> >>> This looks strange.
> >>>
> >>> In ONENAND_DEVICE_DENSITY_2Gb:
> >>> ONENAND_HAS_UNLOCK_ALL is set unconditionally.
> >>>
> >>> But then, under ONENAND_DEVICE_DENSITY_1Gb, the same option is set only
> >>> if process is evaluated to true.
> >>>
> >>> Same problem with ONENAND_HAS_2PLANE:
> >>> - it is set in ONENAND_DEVICE_DENSITY_4Gb only if ONENAND_IS_DDP()
> >>> - it is unset in ONENAND_DEVICE_DENSITY_2Gb only if !ONENAND_IS_DDP()
> >>>
> >>> Maybe this portion should be reworked because I am unsure if this is a
> >>> missing fall through or a bug.
> >>>     
> >>
> >> I wonder if you had the chance to take a look into this piece of code.
> >>
> >> Thanks
> >> --
> >> Gustavo  
> > 
> > What do you mean?
> >   
> 
> You commented that the piece of code above should be reworked. So, it wasn't
> clear to me who was going to do that; and that's why I'm asking if you took
> a look into it and finally determine whether we are dealing with an actual
> bug or a false positive.

Yes please do it, I don't have the time and I don't plan to do it
myself.


Thanks,
Miquèl