Re: [PATCH 4/6] hw_breakpoint: Factor out __modify_user_hw_breakpoint function

[Milind Chabbi]

On Mon, Nov 27, 2017 at 3:07 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
> On Mon, Nov 27, 2017 at 11:01:28PM +0100, Peter Zijlstra wrote:
>> On Mon, Nov 27, 2017 at 01:50:30PM -0800, Milind Chabbi wrote:
>> > The possible checks is infinite
>>
>> struct perf_event_attr is very much a finite data type.
>>
>> Something as simple as:
>>
>>       struct perf_event_attr tmp1 = new_attr, tmp2 = event->attr;
>>
>>       tmp1.bp_type = tmp2.bp_type;
>>       tmp1.bp_addr = tmp2.bp_addr;
>>       tmp1.bp_len  = tmp2.bp_len;
>>
>>       if (memcmp(&tmp1, &tmp2, sizeof(tmp1)))
>>               return -EINVAL;
>>
>> would actually do the checks __modify_user_hw_breakpoint() needs to do.
>
> It could fail with uninitialized padding.
>
>
> -Andi
>

Hm...
How about we zero out __reserved_1 and __reserved_2 before memcmp()?