linux-kernel - Re: [PATCH 4/9] mtd: nand: qcom: fix null pointer access for erased buffer detection

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Message-ID: <20180422182532.221747b6@xps13>
Date:   Sun, 22 Apr 2018 18:25:32 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Abhishek Sahu <absahu@...eaurora.org>
Cc:     Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Archit Taneja <architt@...eaurora.org>,
        Richard Weinberger <richard@....at>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Andy Gross <andy.gross@...aro.org>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 4/9] mtd: nand: qcom: fix null pointer access for erased
 buffer detection

Hi Abhishek,

On Thu, 12 Apr 2018 12:24:16 +0530, Abhishek Sahu
<absahu@...eaurora.org> wrote:

> On 2018-04-10 14:42, Miquel Raynal wrote:
> > Hi Abhishek,  
> > > On Wed,  4 Apr 2018 18:12:20 +0530, Abhishek Sahu  
> > <absahu@...eaurora.org> wrote:  
> > >> parse_read_errors can be called with only oob buf also in which  
> >> case data_buf will be NULL.  If data_buf is NULL, then don’t
> >> treat this page as completely erased in case of ECC uncorrectable
> >> error.  
> >> >> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>  
> >> ---
> >>  drivers/mtd/nand/qcom_nandc.c | 7 +++++--
> >>  1 file changed, 5 insertions(+), 2 deletions(-)  
> >> >> diff --git a/drivers/mtd/nand/qcom_nandc.c >> b/drivers/mtd/nand/qcom_nandc.c  
> >> index 57c16a6..0ebcc55 100644
> >> --- a/drivers/mtd/nand/qcom_nandc.c
> >> +++ b/drivers/mtd/nand/qcom_nandc.c
> >> @@ -1607,9 +1607,11 @@ static int parse_read_errors(struct >> qcom_nand_host *host, u8 *data_buf,
> >>  			if (host->bch_enabled) {
> >>  				erased = (erased_cw & ERASED_CW) == ERASED_CW ?
> >>  					 true : false;
> > > Why the parse_read_errors() function could not be called without  
> > data_buf when using BCH? Are you sure the situation can only happen
> > without it?
> >   
>    host->bch_enabled case is different where controller itself tells
>    regarding erased page in status register.
> 
> > Would the following apply here too, with a:
> >   
>   erased_chunk_check_and_fixup will be used only for 4 bit RS ECC
>   code in which there is no support from HW for erased page detection
>   and we need to check few data bytes value.

So please explain this with a comment.

Thanks,
Miquèl