linux-kernel - Re: drivers/of: crash on boot

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Date:	Wed, 18 May 2016 20:51:59 -0500
From:	Rob Herring <robh@...nel.org>
To:	Rhyland Klein <rklein@...dia.com>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: drivers/of: crash on boot

On Wed, May 18, 2016 at 7:23 PM, Rob Herring <robh@...nel.org> wrote:
> On Wed, May 18, 2016 at 4:26 PM, Rhyland Klein <rklein@...dia.com> wrote:
>> On 5/18/2016 3:58 PM, Rhyland Klein wrote:
>>> On 5/18/2016 3:36 PM, Rob Herring wrote:
>>>> On Wed, May 18, 2016 at 10:34 AM, Sasha Levin <sasha.levin@...cle.com> wrote:
>>>>> Hi Rhyland,
>>>>>
>>>>> I'm seeing a crash on boot that seems to have been caused by
>>>>> "drivers/of: Fix depth when unflattening devicetree":
>>>>>
>>>>> [   61.145229] ==================================================================
>>>>>
>>>>> [   61.147588] BUG: KASAN: stack-out-of-bounds in unflatten_dt_nodes+0x11d2/0x1290 at addr ffff88005b30777c

[...]

>> This patch seems to work for me. I found a bug in my original patch.
>> Sasha/Rob, can you see if this works for you too:
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 0b5850027bb5..e7a8caac5b27 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -407,9 +407,9 @@ static int unflatten_dt_nodes(const void *blob,
>>
>>         root = dad;
>>         fpsizes[depth] = dad ? strlen(of_node_full_name(dad)) : 0;
>> -       nps[depth+1] = dad;
>> +       nps[depth] = dad;
>>         for (offset = 0;
>> -            offset >= 0;
>> +            offset >= 0 && depth >= 0;
>>              offset = fdt_next_node(blob, offset, &depth)) {
>>                 if (WARN_ON_ONCE(depth >= FDT_MAX_DEPTH))
>>                         continue;
>
> This is not work for me. I'm booting x86 with the DT unit test and
> KASAN enabled. I suspect our differences are due to different data
> after the end of the dtb. Also, I think there may be a bug in
> fdt_next_node FDT_END handling. The "!depth" seems suspicious to me
> and I think it should be "!(*depth)".
>
> The DT overlay unit tests are also failing. Not sure if that's related.

Seems with the above patch and the fix to fdt_next_node, the problem
is fixed both for KASAN and the DT overlay tests. Trying it out now
with some other configurations.

Rob