Re: [PATCH] of: overlay: set 'overlay_tree' and 'fdt' fields only on success

[Frank Rowand <frowand.list@gmail.com>]

On 4/4/22 15:38, Rob Herring wrote:
> On Thu, Mar 31, 2022 at 11:56:33AM +0200, Slawomir Stepien wrote:
>> From: Slawomir Stepien <slawomir.stepien@nokia.com>
>>
>> Before this change, the memory pointed by fields 'overlay_tree' and
>> 'fdt' will be double freed by a call to free_overlay_changeset() from
>> of_overlay_apply(), when the init_overlay_changeset() fails.
>>
>> The first free will happen under 'err_free_tree' label and for the
>> second time under 'err_free_overlay_changeset' label, where we call
>> free_overlay_changeset().
>>
>> This could happen for example, when you are applying an overlay to a
>> target path that does not exists.
>>
>> By setting the pointers only when we are sure that
>> init_overlay_changeset() will not fail, will prevent this double free.
> 
> It looks to me like the free should just be moved from 
> init_overlay_changeset() to of_overlay_fdt_apply() where the allocation 
> is done. Frank?

This patch is next on my list to look over.

-Frank

> 
> Also, I believe there's a bug that of_overlay_apply() should be passed 
> new_fdt_align rather than new_fdt. It's only a bug if we expect 
> overlay_changeset.fdt to point to a valid fdt rather than the memory 
> allocation.
> 
> Rob