On 12/09/17 01:04, Geert Uytterhoeven wrote:
> Hi Frank,
>
> On Sat, Dec 9, 2017 at 7:01 AM, Frank Rowand <frowand.list@xxxxxxxxx> wrote:
>> On 12/08/17 05:13, Geert Uytterhoeven wrote:
>>> This patch series fixes memory corruption when applying overlays.
>>> I first noticed this when using OF configfs. After lots of failed
>>> debugging attempts, I bisected it to "of: overlay: add per overlay sysfs
>>> attributes", which is not upstream. But that was a red herring: that
>>> commit enlarged struct fragment to exactly 64-bytes, which just made it
>>> more likely to cause random corruption when writing beyond the end of an
>>> array of fragment structures. With the smaller structure size before,
>>> such writes usually ended up in the unused holes between allocated
>>> blocks, causing no harm.
>>>
>>> The first patch is the real fix, and applies to both v4.15-rc2 and Rob's
>>> for-next branch.
>>> The second patch is a small improvement, and applies to Rob's for-next
>>> branch only.
>>
>> Overlay FDT files should not have invalid contents. But they inevitably
>> will, so the code has to handle those cases. Thanks for finding this
>> problem and making the code better!
>
> Sure, people can throw anything at it ;-)
>
> In my case, I'm wondering if the dtbo was actually invalid?
> Simplification of the decompiled dtbo:
>
> /dts-v1/;
>
> / {
>
> fragment-name {
> target-path = [2f 00];
>
> __overlay__ {
>
> node-name {
> compatible = "foo,bar";
> gpios = <0xffffffff 0x0 0x0>;
> };
> };
> };
>
> __fixups__ {
> bank0 = "/fragment-name/__overlay__/node-name:gpios:0";
> };
> };
>
> So it has __fixup__, but no __symbols__, which looks totally valid to me.
Yes, that is correct. The bug would also be exposed if there was a __local_fixups__
node without a __symbols__ node. Which is also a valid overlay.
My comment was triggered by another possible case, where a non-overlay node
occurs in an overlay, without a __symbols__ node. I'm not positive, but I
don't think that dtc would find an error in that case.
>> For the full series:
>>
>> Reviewed-by: Frank Rowand <frank.rowand@xxxxxxxx>
>
> Thanks!
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>
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