Re: [Qemu-devel] [PATCH 3/3 v2] ppc debug: Add debug stub support

[Alexander Graf <agraf@suse.de>]

On 17.06.14 13:01, Bharat.Bhushan@freescale.com wrote:
>>>>>>> +static void kvm_arch_e500_update_guest_debug(CPUState *cs,
>>>>>>> +                                             struct
>>>>>>> +kvm_guest_debug
>>>>>>> +*dbg) {
>>>>>>> +    int n;
>>>>>>> +
>>>>>>> +    if (nb_hw_breakpoint + nb_hw_watchpoint > 0) {
>>>>>>> +        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP;
>>>>>>> +        memset(dbg->arch.bp, 0, sizeof(dbg->arch.bp));
>>>>>>> +        for (n = 0; n < nb_hw_breakpoint + nb_hw_watchpoint; n++)
>>>>>>> + {
>>>>>> Boundary check against dbg->arch.bp missing.
>>>>> Did not get, what you mean by " dbg->arch.bp missing" ?
>>>> dbg->arch.bp is an array of a certain size. If nb_hw_breakpoint +
>>>> nb_hw_watchpoint > ARRAY_SIZE(dbg->arch.bp) we might overwrite memory
>>>> we don't want to overwrite.
>>> Actually this will never overflow here because nb_hw_breakpoint and
>> nb_hw_watchpoint overflow in taken care in in hw_insert_breakpoint().
>>> Do you thing that to be double safe we can add a check?
>> We only check against an overflow of hw_breakpoint[], not dbg->arch.bp.
>> What if nb_hw_breakpoint becomes 17?
> nb_hw_breakpoint can never be more than max_hw_breakpoint, how nb_hw_breakpoint can be 17 ?

Someone comes along and bumps up max_hw_breakpoint to 17? Just add an 
assert() somewhere that makes sure we can't run over bp :).


Alex