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/openbmc/linux/fs/proc/
H A Dbase.cb95c35e7 Thu Apr 01 08:13:57 CDT 2010 Oleg Nesterov <oleg@redhat.com> 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>