Re: [Qemu-devel] [PATCH] linux-user: Simplify boundary checks on g_posix_timers range

[Alexander Graf <agraf@suse.de>]

On 22.08.14 13:44, Peter Maydell wrote:
> On 22 August 2014 12:42, Alexander Graf <agraf@suse.de> wrote:
>> On 22.08.14 13:33, Peter Maydell wrote:
>>> On 22 August 2014 12:19, Alexander Graf <agraf@suse.de> wrote:
>>>> We check whether the passed in counter value is negative on all calls
>>>> that involve g_posix_timers. However, we AND the value down to 16 bits
>>>> right before the check, so they can never be negative.
>>>
>>> ...but why exactly are we doing that AND with 0xffff ?? It seems
>>> unlikely that the kernel really allows random garbage in the top
>>> half of the timer ID arguments, so maybe we should drop the
>>> mask and keep the <0 bounds checks?
>>
>> Or we drop the AND and and the <0 check and treat arg1 as unsigned ;).
> 
> That probably just requires equally many changes to
> code that is currently correct because the arg* are
> signed but would need changes if they became unsigned.

Well, I do have a downstream patch that makes them unsigned, so I'd
rather like to make the code as stable to that as I can ;).


Alex