Commit b95c35e7 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

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: default avatarOleg Nesterov <>
Signed-off-by: default avatarLinus Torvalds <>
parent 30d1872d
......@@ -442,12 +442,13 @@ static const struct file_operations proc_lstats_operations = {
unsigned long badness(struct task_struct *p, unsigned long uptime);
static int proc_oom_score(struct task_struct *task, char *buffer)
unsigned long points;
unsigned long points = 0;
struct timespec uptime;
points = badness(task->group_leader, uptime.tv_sec);
if (pid_alive(task))
points = badness(task, uptime.tv_sec);
return sprintf(buffer, "%lu\n", points);
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