linux-kernel - Re: [PATCH v2] mtdoops: Fix the size of the header read buffer.

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Date:   Thu, 3 Feb 2022 17:53:47 -0800
From:   Jean-Marc Eurin <jmeurin@...gle.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mtdoops: Fix the size of the header read buffer.

On Mon, Jan 31, 2022 at 2:00 AM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>
> Hi Jean-Marc,
>
> jmeurin@...gle.com wrote on Fri, 28 Jan 2022 14:01:56 -0800:
>
> > The read buffer size depends on the MTDOOPS_HEADER_SIZE.
> >
> > Tested: Changed the header size, it doesn't panic, header is still
> > read/written correctly.
>
> On what Linux kernel version are you? It looks like we don't share the
> same code base, are we?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mtd/mtdoops.c?h=v5.17-rc2
has that bug.  If you try to increase the MTDOOPS_HEADER_SIZE,
find_next_position() will try to do an mtd_read() of
MTDOOPS_HEADER_SIZE bytes in a count buffer that is fixed to only 8
bytes.

Thanks,

Jean-Marc

>
> >
> > Signed-off-by: Jean-Marc Eurin <jmeurin@...gle.com>
> > ---
> >  drivers/mtd/mtdoops.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
> > index 227df24387df..09a26747f490 100644
> > --- a/drivers/mtd/mtdoops.c
> > +++ b/drivers/mtd/mtdoops.c
> > @@ -223,7 +223,7 @@ static void find_next_position(struct mtdoops_context *cxt)
> >  {
> >       struct mtd_info *mtd = cxt->mtd;
> >       int ret, page, maxpos = 0;
> > -     u32 count[2], maxcount = 0xffffffff;
> > +     u32 count[MTDOOPS_HEADER_SIZE/sizeof(u32)], maxcount = 0xffffffff;
> >       size_t retlen;
> >
> >       for (page = 0; page < cxt->oops_pages; page++) {
>
>
> Thanks,
> Miquèl