Re: [Qemu-stable] [PATCH v5 05/11] linux-user: fix mmap/munmap/mprotect/mremap/shmat

[Max Filippov]

On Wed, Mar 7, 2018 at 2:08 AM, Laurent Vivier <address@hidden> wrote:
>> +static inline int guest_range_valid(unsigned long start, unsigned long len)
>> +{
>> +    if (len)
>> +        return guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 
>> 1;
>> +    else
>> +        return guest_addr_valid(start);
>> +}
>
> I think we can consider len == 0 is invalid and use only:
>
>   return start + (len - 1) <= GUEST_ADDR_MAX;

start + len - 1 may wrap around, that's why I first validate len and then have
len at the right side of the comparison. I.e. if we drop check for len == 0 I'd
still write it as

  guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;

-- 
Thanks.
-- Max