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

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Message-ID: <CAL_JsqL_8cUmKxu3=BBkmFi3yO7rWeUW64TO6MRV60451V70+Q@mail.gmail.com>
Date:	Thu, 19 May 2016 07:48:18 -0500
From:	Rob Herring <robh@...nel.org>
To:	Gavin Shan <gwshan@...ux.vnet.ibm.com>
Cc:	Rhyland Klein <rklein@...dia.com>,
	Sasha Levin <sasha.levin@...cle.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 Thu, May 19, 2016 at 6:19 AM, Gavin Shan <gwshan@...ux.vnet.ibm.com> wrote:
> On Wed, May 18, 2016 at 08:51:59PM -0500, Rob Herring wrote:
>>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.
>>
>
> There're 5 patches I introduced to drivers/of/fdt.c (A). Rhyland had
> one patch based on them (B). The code change in this thread is (C).
> I tried several cases as below.
>
> There is one failing case caused by something we don't know yet. I
> will do some invetigation unless it's not a issue or a known issue
> of unittest itself.
>
> [1]. (A) excluded, (B) excluded, (C) excluded
> =============================================
> device-tree: Duplicate name in testcase-data, renamed to "duplicate-name#1"
> ### dt-test ### start of unittest - you will see error messages
> /testcase-data/phandle-tests/consumer-a: could not get #phandle-cells-missing for /testcase-data/phandle-tests/provider1
> /testcase-data/phandle-tests/consumer-a: could not get #phandle-cells-missing for /testcase-data/phandle-tests/provider1
> /testcase-data/phandle-tests/consumer-a: could not find phandle
> /testcase-data/phandle-tests/consumer-a: could not find phandle
> /testcase-data/phandle-tests/consumer-a: arguments longer than property
> /testcase-data/phandle-tests/consumer-a: arguments longer than property
> irq: XICS didn't like hwirq-0x1 to VIRQ32 mapping (rc=-22)
> irq: XICS didn't like hwirq-0x1 to VIRQ32 mapping (rc=-22)
> ### dt-test ### FAIL of_unittest_platform_populate():783 device deferred probe failed - 0

Humm, I'm not seeing this one.

> overlay_is_topmost: #5 clashes #6 @/testcase-data/overlay-node/test-bus/test-unittest8
> overlay_removal_is_ok: overlay #5 is not topmost
> of_overlay_destroy: removal check failed for overlay #5
> ### dt-test ### end of unittest - 147 passed, 1 failed
>
> [2]. (A) included, (B) exsluded, (C) excluded
> =============================================
> Same output as [1]
>
> [3]. (A) included, (B) included, (C) excluded
> =============================================
> System fails to boot
>
> [4]. (A) included, (B) included, (C) included
> =============================================
> Same output as [1] and [2].

For C, this includes the fix to depth in fdt_next_node?

While case 2 works for you, do you agree that there is an off by one
error and initially fdt_next_node should be called with depth=0?

Rob