linux-kernel - Re: [PATCH 1/1] mtd: nand: add check for out of page read

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Date:	Sun, 19 Dec 2010 18:54:05 +0200
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Jason Liu <liu.h.jason@...il.com>
Cc:	Jason Liu <r64343@...escale.com>, David.Woodhouse@...el.com,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mtd: nand: add check for out of page read

On Wed, 2010-12-15 at 09:55 +0800, Jason Liu wrote:
> >        /* Do not allow reads past end of device */
> >        if (unlikely(from >= mtd->size ||
> >                     ops->ooboffs + readlen > ((mtd->size >> chip->page_shift) -
> >                                        (from >> chip->page_shift)) * len)) {
> >                DEBUG(MTD_DEBUG_LEVEL0, "%s: Attempt read beyond end "
> >                                        "of device\n", __func__);
> >                return -EINVAL;
> >        }
> 
> Here the mtd->size in nand_base.c should be the NAND flash chip size,

I think this is partition size as well.

> while in nand_oobtest,
> 
>               /* Attempt to read off end of device */
>                 ops.mode      = MTD_OOB_AUTO;
>                 ops.len       = 0;
>                 ops.retlen    = 0;
>                 ops.ooblen    = mtd->ecclayout->oobavail;
>                 ops.oobretlen = 0;
>                 ops.ooboffs   = 1;
>                 ops.datbuf    = NULL;
>                 ops.oobbuf    = readbuf;
>                 printk(PRINT_PREF "attempting to read past end of device\n");
>                 printk(PRINT_PREF "an error is expected...\n");
>                 err = mtd->read_oob(mtd, mtd->size - mtd->writesize, &ops);
>                 if (err) {
>                         printk(PRINT_PREF "error occurred as expected\n");
>                         err = 0;
>                 } else {
>                         printk(PRINT_PREF "error: read past end of device\n");
>                         errcnt += 1;
>                 }
>         }
> 
> here, mtd->size is mtd partition size right? when the mtd partition is
> not the last MTD partition, the error will happen.

I think this is the same in both. Try to debug this with printks().

> 
> I have tested on real NAND, while not on nandsim.

Please, try to reproduce this with nandsim as well, and if it works, try
to find out why (using printk debugging)

-- 
Best Regards,
Artem Bityutskiy (Битюцкий Артём)

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