lkml.org 
[lkml]   [2011]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 3/3] pids: Make it possible to clone tasks with given pids
    On 11/10, Pavel Emelyanov wrote:
    >
    > The child_tidptr points to an array of pids for current namespace and
    > its ancestors. When 0 is met in this array the pid number for the
    > corresponding namespace is generated, rather than set.

    I must have missed something, but I can't unserstand how this works.

    > For security reasons after a regular clone/fork is done in a namespace
    > further cloning with predefined pid is not allowed.

    I guess, this is pid_ns->last_pid != 0 check in set_pidmap(), right ?

    > +static int set_pidmap(struct pid_namespace *pid_ns, int pid)
    > +{
    > + int offset;
    > + struct pidmap *map;
    > +
    > + offset = pid & BITS_PER_PAGE_MASK;
    > + map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
    > +
    > + if (unlikely(!map->page))
    > + if (alloc_pidmap_page(map))
    > + return -ENOMEM;
    > +
    > + if (pid_ns->last_pid != 0)
    > + return -EPERM;

    OK, but it should be always true, no? IOW, set_pidmap() should always
    fail?

    Unless: you are using CLONE_NEWPID along with CLONE_CHILD_USEPIDS and
    this child_tidptr array has only one pid (before zero pid).

    So, could you please explain what I have missed?

    Oleg.



    \
     
     \ /
      Last update: 2011-11-10 19:53    [W:0.021 / U:0.568 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site