• Eric W. Biederman's avatar
    [PATCH] Make setsid() more robust · 390e2ff0
    Eric W. Biederman authored
    The core problem: setsid fails if it is called by init.  The effect in 2.6.16
    and the earlier kernels that have this problem is that if you do a "ps -j 1 or
    ps -ej 1" you will see that init and several of it's children have process
    group and session == 0.  Instead of process group == session == 1.  Despite
    init calling setsid.
    The reason it fails is that daemonize calls set_special_pids(1,1) on kernel
    threads that are launched before /sbin/init is called.
    The only remaining effect in that current->signal->leader == 0 for init
    instead of 1.  And the setsid call fails.  No one has noticed because
    /sbin/init does not check the return value of setsid.
    In 2.4 where we don't have the pidhash table, and daemonize doesn't exist
    setsid actually works for init.
    I care a lot about pid == 1 not being a special case that we leave broken,
    because of the container/jail work that I am doing.
    - Carefully allow init (pid == 1) to call setsid despite the kernel using
      its session.
    - Use find_task_by_pid instead of find_pid because find_pid taking a
      pidtype is going away.
    Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>