• Tetsuo Handa's avatar
    Add RCU check for find_task_by_vpid(). · 4221a991
    Tetsuo Handa authored
    find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to
    commit 3120438a "rcu: Disable lockdep checking in RCU list-traversal primitives",
    we are currently unable to catch "find_task_by_vpid() with tasklist_lock held
    but RCU lock not held" errors due to the RCU-lockdep checks being
    suppressed in the RCU variants of the struct list_head traversals.
    This commit therefore places an explicit check for being in an RCU
    read-side critical section in find_task_by_pid_ns().
      [ INFO: suspicious rcu_dereference_check() usage. ]
      kernel/pid.c:386 invoked rcu_dereference_check() without protection!
      other info that might help us debug this:
      rcu_scheduler_active = 1, debug_locks = 1
      1 lock held by rc.sysinit/1102:
       #0:  (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160
      stack backtrace:
      Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1
      Call Trace:
       [<c105e714>] lockdep_rcu_dereference+0x94/0xb0
       [<c104b4cd>] find_task_by_pid_ns+0x6d/0x70
       [<c104b4e8>] find_task_by_vpid+0x18/0x20
       [<c1048347>] sys_setpgid+0x47/0x160
       [<c1002b50>] sysenter_do_call+0x12/0x36
    Commit updated to use a new rcu_lockdep_assert() exported API rather than
    the old internal __do_rcu_dereference().
    Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
pid.c 13.7 KB