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

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Message-ID: <20160519111950.GA28855@gwshan>
Date:	Thu, 19 May 2016 21:19:51 +1000
From:	Gavin Shan <gwshan@...ux.vnet.ibm.com>
To:	Rob Herring <robh@...nel.org>
Cc:	Rhyland Klein <rklein@...dia.com>,
	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 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
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].

(A):   8326241 drivers/of: Return allocated memory from of_fdt_unflatten_tree()
       c426323 drivers/of: Specify parent node in of_fdt_unflatten_tree()
       947c82c drivers/of: Rename unflatten_dt_node()
       5080008 drivers/of: Avoid recursively calling unflatten_dt_node()
       dfbd4c6 drivers/of: Split unflatten_dt_node()
(B):   ac78f9b drivers/of: Fix depth when unflattening devicetree

Thanks,
Gavin
 
>Rob
>