Messages in this thread | | | Subject | Re: [RFC c/r 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7 | From | "" <> | Date | Fri, 27 Jan 2012 11:59:18 -0800 |
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No, cookies[1] is always odd.
Vasiliy Kulikov <segoon@openwall.com> wrote:
>Hi Cyrill, > >On Fri, Jan 27, 2012 at 21:53 +0400, Cyrill Gorcunov wrote: >> +/* >> + * We don't expose real in-memory order of objects for security >> + * reasons, still the comparision results should be suitable for >> + * sorting. Thus, we obfuscate kernel pointers values (using random >> + * cookies obtaned at early boot stage) and compare the production >> + * instead. >> + */ >> +static unsigned long cookies[KCMP_TYPES][2] __read_mostly; >> + >> +static long kptr_obfuscate(long v, int type) >> +{ >> + return (v ^ cookies[type][0]) * cookies[type][1]; > >AFACS, cookies is fully random value, is it possible that > >((v1 ^ cookies[type][0]) * cookies[type][1] == (v2 ^ cookies[type][0]) >* cookies[type][1]) && >(v1 != v2) > >for too round cookies[type][1]? > >Thanks, > >-- >Vasiliy Kulikov >http://www.openwall.com - bringing security into open computing >environments
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