Commit d19d5476 authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

oom: fix locking for oom_adj and oom_score_adj 



The locking order in oom_adjust_write() and oom_score_adj_write() for
task->alloc_lock and task->sighand->siglock is reversed, and lockdep
notices that irqs could encounter an ABBA scenario.

This fixes the locking order so that we always take task_lock(task) prior
to lock_task_sighand(task).

Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Reported-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 723548bf

fs/proc/base.c

+21 −19
Original line number Diff line number Diff line
@@ -1042,9 +1042,16 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf, 
		err = -ESRCH;

		goto out;

	}



	task_lock(task);

	if (!task->mm) {

		err = -EINVAL;

		goto err_task_lock;

	}



	if (!lock_task_sighand(task, &flags)) {

		err = -ESRCH;

		goto err_task_struct;

		goto err_task_lock;

	}



	if (oom_adjust < task->signal->oom_adj && !capable(CAP_SYS_RESOURCE)) {
@@ -1052,12 +1059,6 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf, 
		goto err_sighand;

	}



	task_lock(task);

	if (!task->mm) {

		err = -EINVAL;

		goto err_task_lock;

	}



	if (oom_adjust != task->signal->oom_adj) {

		if (oom_adjust == OOM_DISABLE)

			atomic_inc(&task->mm->oom_disable_count);
@@ -1083,11 +1084,10 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf, 
	else

		task->signal->oom_score_adj = (oom_adjust * OOM_SCORE_ADJ_MAX) /

								-OOM_DISABLE;

err_task_lock:

	task_unlock(task);

err_sighand:

	unlock_task_sighand(task, &flags);

err_task_struct:

err_task_lock:

	task_unlock(task);

	put_task_struct(task);

out:

	return err < 0 ? err : count;
@@ -1150,21 +1150,24 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, 
		err = -ESRCH;

		goto out;

	}



	task_lock(task);

	if (!task->mm) {

		err = -EINVAL;

		goto err_task_lock;

	}



	if (!lock_task_sighand(task, &flags)) {

		err = -ESRCH;

		goto err_task_struct;

		goto err_task_lock;

	}



	if (oom_score_adj < task->signal->oom_score_adj &&

			!capable(CAP_SYS_RESOURCE)) {

		err = -EACCES;

		goto err_sighand;

	}



	task_lock(task);

	if (!task->mm) {

		err = -EINVAL;

		goto err_task_lock;

	}

	if (oom_score_adj != task->signal->oom_score_adj) {

		if (oom_score_adj == OOM_SCORE_ADJ_MIN)

			atomic_inc(&task->mm->oom_disable_count);
@@ -1181,11 +1184,10 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, 
	else

		task->signal->oom_adj = (oom_score_adj * OOM_ADJUST_MAX) /

							OOM_SCORE_ADJ_MAX;

err_task_lock:

	task_unlock(task);

err_sighand:

	unlock_task_sighand(task, &flags);

err_task_struct:

err_task_lock:

	task_unlock(task);

	put_task_struct(task);

out:

	return err < 0 ? err : count;

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