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

[Abhishek Sahu]

On 2018-04-22 21:55, Miquel Raynal wrote:
> Hi Abhishek,
>
> On Thu, 12 Apr 2018 12:24:16 +0530, Abhishek Sahu
> <absahu@xxxxxxxxxxxxxx> wrote:
>
> > On 2018-04-10 14:42, Miquel Raynal wrote:
> > > Hi Abhishek,
> > > > On Wed,  4 Apr 2018 18:12:20 +0530, Abhishek Sahu
> > > <absahu@xxxxxxxxxxxxxx> 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 donât
> > >> treat this page as completely erased in case of ECC uncorrectable
> > >> error.
> > >> >> Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx>
> > >> ---
> > >>  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,
> MiquÃl

 Sure Miquel.
 I will do the same and update the patch with more comments.

 Thanks,
 Abhishek