oom: fix the unsafe usage of badness() in proc_oom_score()
authorOleg Nesterov <oleg@redhat.com>
Thu, 1 Apr 2010 13:13:57 +0000 (15:13 +0200)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 1 Apr 2010 15:50:21 +0000 (08:50 -0700)
commitb95c35e76b29ba812e5dabdd91592e25ec640e93
tree9584cf21e47baec986f5dc5455081e8538126be1
parent30d1872d9eb3663b4cf7bdebcbf5cd465674cced
oom: fix the unsafe usage of badness() in proc_oom_score()

proc_oom_score(task) has a reference to task_struct, but that is all.
If this task was already released before we take tasklist_lock

- we can't use task->group_leader, it points to nowhere

- it is not safe to call badness() even if this task is
  ->group_leader, has_intersects_mems_allowed() assumes
  it is safe to iterate over ->thread_group list.

- even worse, badness() can hit ->signal == NULL

Add the pid_alive() check to ensure __unhash_process() was not called.

Also, use "task" instead of task->group_leader. badness() should return
the same result for any sub-thread. Currently this is not true, but
this should be changed anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/proc/base.c