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    SubjectRe: [patch 1/4] Add routine for generating an ID for kernel pointer
    Hello, Cyrill.

    Just my 2 cents.

    On Fri, Dec 23, 2011 at 04:47:42PM +0400, Cyrill Gorcunov wrote:
    > +unsigned long gen_obj_id(void *ptr, int type)
    > +{
    > + if (!capable(CAP_SYS_ADMIN) || !ptr)
    > + return 0;
    > +
    > + BUG_ON(type >= GEN_OBJ_ID_TYPES);
    > +
    > + /*
    > + * Note the simple XOR is used here not in a sake
    > + * of security by any means, but rather to break
    > + * an "impression" that such IDs means something
    > + * other than a number which can be used for comparison
    > + * with another number generated by this helper only.
    > + */
    > + return ((unsigned long)ptr) ^ gen_obj_cookie[type];
    > +}

    To me, XOR & CAP_SYS_ADMIN combination doesn't make much sense. With
    CAP_SYS_ADMIN, there's no reason for XOR - we can just export
    pointers. If we plan on removing CAP_SYS_ADMIN restriction down the
    road, XOR doesn't help much. It's too weak. The XOR is unnecessary
    with CAP_SYS_ADMIN and useless without it. It seems pointless to me.
    If we're going down this route, I think doing cryptographically safe
    hash would be much better.

    Thanks.

    --
    tejun


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