• Oleg Nesterov's avatar
    kernel/fork.c:copy_process(): don't add the uninitialized child to thread/task/pid lists · 81907739
    Oleg Nesterov authored
    copy_process() adds the new child to thread_group/init_task.tasks list and
    then does attach_pid(child, PIDTYPE_PID).  This means that the lockless
    next_thread() or next_task() can see this thread with the wrong pid.  Say,
    "ls /proc/pid/task" can list the same inode twice.
    
    We could move attach_pid(child, PIDTYPE_PID) up, but in this case
    find_task_by_vpid() can find the new thread before it was fully
    initialized.
    
    And this is already true for PIDTYPE_PGID/PIDTYPE_SID, With this patch
    copy_process() initializes child->pids[*].pid first, then calls
    attach_pid() to insert the task into the pid->tasks list.
    
    attach_pid() no longer need the "struct pid*" argument, it is always
    called after pid_link->pid was already set.
    Signed-off-by: 's avatarOleg Nesterov <oleg@redhat.com>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: Pavel Emelyanov <xemul@parallels.com>
    Cc: Sergey Dyasly <dserrg@gmail.com>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    81907739
pid.h 5.78 KB