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>
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@ -442,12 +442,13 @@ static const struct file_operations proc_lstats_operations = {
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unsigned long badness(struct task_struct *p, unsigned long uptime);
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static int proc_oom_score(struct task_struct *task, char *buffer)
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{
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unsigned long points;
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unsigned long points = 0;
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struct timespec uptime;
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do_posix_clock_monotonic_gettime(&uptime);
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read_lock(&tasklist_lock);
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points = badness(task->group_leader, uptime.tv_sec);
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if (pid_alive(task))
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points = badness(task, uptime.tv_sec);
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read_unlock(&tasklist_lock);
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return sprintf(buffer, "%lu\n", points);
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}
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