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

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Message-ID: <d0e2564c-c8d4-2c4c-f194-60b43b0ab80e@nvidia.com>
Date:	Wed, 18 May 2016 17:26:39 -0400
From:	Rhyland Klein <rklein@...dia.com>
To:	Rob Herring <robh@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Gavin Shan" <gwshan@...ux.vnet.ibm.com>
CC:	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 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
>>
>> The following appears to fix it for me. Rhyland, please confirm.
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 7f38241..888ec2a 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -409,7 +409,7 @@ static int unflatten_dt_nodes(const void *blob,
>>         fpsizes[depth] = dad ? strlen(of_node_full_name(dad)) : 0;
>>         nps[depth+1] = 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;
>>
> 
> If I try that patch, i see this when compiling:
> 
> In function ‘unflatten_dt_nodes’:
> warning: left-hand operand of comma expression has no effect
> [-Wunused-value]
> 	offset >= 0, depth >= 0;
> 

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;

-rhyland


-- 
nvpublic