Re: [Query] Stack Overflow in "arch/arm/kernel/unwind.c" whileunwinding frame

[Anurag Aggarwal]

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@xxxxxxxxxx> 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@xxxxxxxxx> 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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