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

[Jean Pihet]

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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