Re: Patch to solve NULL pointer dereference in physmap_of.c

[Artem Bityutskiy <dedekind1@gmail.com>]

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Hi, sorry for long delay, but would you please re-send this in a nice
form:

1. Wrap commit message lines to 80 characters.
2. Make the patch applicable with 'git am' - this one does not apply.

Thanks!

On Thu, 2012-11-22 at 16:20 +0100, Prins Anton (ST-CO/ENG1.1) wrote:
> [PATCH] mtd: maps/physmap_of.c: change error checking to prevent a NULL pointer dereference if no DTS tuple is mappable
> 
> This patch solves a NULL pointer dereference, this may occur if the tuple is not mappable (jumps to continue in the for-loop).
> Out of the loop possible results are: 
> - info->list_size == 0  if no of the tuples is mappable
> - info->list_size == 1
> - info->list_size > 1
> If no one of the supplied tuples is mappable (info->list_size == 0) and info->cmtd will not be set.
> But it is used in mtd_device_parse_register, OOPS... if should generate an error in this case!
> 
> [From: Anton Prins <anton.prins@nl.bosch.com>]
> 
> diff --git a/drivers/mtd/maps/physmap_of.c b/drivers/mtd/maps/physmap_of.c
> index 2e6fb68..f6de444 100644
> --- a/drivers/mtd/maps/physmap_of.c
> +++ b/drivers/mtd/maps/physmap_of.c
> @@ -268,6 +268,7 @@ static int __devinit of_flash_probe(struct platform_device *dev)
>         }
> 
>         err = 0;
> +       info->cmtd = NULL;
>         if (info->list_size == 1) {
>                 info->cmtd = info->list[0].mtd;
>         } else if (info->list_size > 1) {
> @@ -276,9 +277,10 @@ static int __devinit of_flash_probe(struct platform_device *dev)
>                  */
>                 info->cmtd = mtd_concat_create(mtd_list, info->list_size,
>                                                dev_name(&dev->dev));\r-               if (info->cmtd == NULL)
> -                       err = -ENXIO;
>         }
> +       if (info->cmtd == NULL)
> +               err = -ENXIO;
> +
>         if (err)
>                 goto err_out;
> 
> -----Original Message-----
> From: Artem Bityutskiy [mailto:dedekind1@gmail.com] 
> Sent: woensdag 21 november 2012 8:42
> To: Prins Anton (ST-CO/ENG1.1)
> Cc: linux-mtd@lists.infradead.org
> Subject: Re: Patch to solve NULL pointer dereference in physmap_of.c
> On Fri, 2012-11-09 at 08:45 +0100, Prins Anton (ST-CO/ENG1.1) wrote:\r> commit 0905a6f4aec377123e94d2260f2f7a0d867e19be
> > Author: Anton Prins <anton.prins@nl.bosch.com>
> > Date:   Fri Nov 9 10:12:58 2012 +0100
> > 
> >     Correct error checking to prevent a NULL pointer dereference
> > 
> >     The problem only occurs if the DTS is not correct, the requested mapping is not reserved on the parent bus.
> >     In this special case the count is 1, but the list_size after mapping is 0. list_size 0 should generate an error!
> 
> Sorry, I do not really understand which problem this patch solves, could
> you please improve the commit message and re-send?
> 
> > 
> > diff --git a/drivers/mtd/maps/physmap_of.c b/drivers/mtd/maps/physmap_of.c
> > index 2e6fb68..83d121e 100644
> > --- a/drivers/mtd/maps/physmap_of.c
> > +++ b/drivers/mtd/maps/physmap_of.c
> > @@ -267,13 +267,14 @@ static int __devinit of_flash_probe(struct platform_device *dev)
> >                 info->list[i].mtd->dev.parent = &dev->dev;
> >         }
> > 
> 
> It seems the error condition should be checked and acted upon here. What
> you looks more like making the code less readable.
> 
> > -       err = 0;
> >         if (info->list_size == 1) {
> > +               err = 0;
> >                 info->cmtd = info->list[0].mtd;
> >         } else if (info->list_size > 1) {
> >                 /*
> >                  * We detected multiple devices. Concatenate them together.
> >                  */
> > +               err = 0;
> >                 info->cmtd = mtd_concat_create(mtd_list, info->list_size,
> >                                                dev_name(&dev->dev));\r>                 if (info->cmtd == NULL)
> 

-- 
Best Regards,
Artem Bityutskiy

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