linux-kernel - Re: [Query] Stack Overflow in "arch/arm/kernel/unwind.c" while unwinding frame

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Message-ID: <CAPoNrtsrTVA+mcYUO_0bRa9vHBPsfrLh6aGHGzZANTX_gO3VTw@mail.gmail.com>
Date:	Tue, 24 Sep 2013 11:59:30 +0530
From:	Anurag Aggarwal <anurag19aggarwal@...il.com>
To:	Jean Pihet <jean.pihet@...aro.org>
Cc:	linux@....linux.org.uk,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Query] Stack Overflow in "arch/arm/kernel/unwind.c" while
 unwinding frame

Hi Jean,

I don't think that it is related to the warning that you have suggested

On Tue, Sep 24, 2013 at 11:58 AM, Jean Pihet <jean.pihet@...aro.org> wrote:
> Hi,
>
> Adding Russell and l.a.k ML.
>
> Another question: is this linked to the following build warning?
>   CC      arch/arm/kernel/return_address.o
> arch/arm/kernel/return_address.c:63:2: warning: #warning "TODO:
> return_address should use unwind tables"
>
> Regards,
> Jean
>
> On 24 September 2013 07:23, Anurag Aggarwal <anurag19aggarwal@...il.com> wrote:
>> Hi All,
>>
>> While executing unwind backtrace instructions in ARM, in the function
>> unwind_exec_insn()
>> there are chances that SP overflows from stack.
>>
>>
>> For example while executing instruction with opcode 0xAE, vsp can go
>> beyond stack to area that has not been allocated till now.
>>
>> unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
>> int reg;
>>
>> /* pop R4-R[4+bbb] */
>> for (reg = 4; reg <= 4 + (insn & 7); reg++)
>> ctrl->vrs[reg] = *vsp++;
>>
>> The above scenario can happen while executing any of the unwind instruction.
>>
>> One of the ways to fix the problem is to check for vsp with stack
>> limits before we increment it, but doing it for all the instructions
>> seems a little bad.
>>
>> I just want to know that if anyone has faced the problem before
>>
>> I am working on Linux kernel for Android phones and I saw one case
>> when this happened.
>>
>> I am new to Linux Kernel so not sure if this is the right place to ask
>> the question.
>>
>>
>> --
>> Anurag Aggarwal
>> --
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-- 
Anurag Aggarwal
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