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oom: fix locking for oom_adj and oom_score_adj

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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: David Rientjes <rientjes@google.com>
Reported-by: Andrew 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2010-10-26 14:21:26 -07:00 committed by Linus Torvalds
parent 723548bff1
commit d19d5476f4
1 changed files with 26 additions and 24 deletions
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50
fs/proc/base.c
View file

@ -1042,15 +1042,6 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
err = -ESRCH;
goto out;
}
if (!lock_task_sighand(task, &flags)) {
err = -ESRCH;
goto err_task_struct;
}
if (oom_adjust < task->signal->oom_adj && !capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
goto err_sighand;
}
task_lock(task);
if (!task->mm) {
@ -1058,6 +1049,16 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
goto err_task_lock;
}
if (!lock_task_sighand(task, &flags)) {
err = -ESRCH;
goto err_task_lock;
}
if (oom_adjust < task->signal->oom_adj && !capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
goto err_sighand;
}
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;
}
if (!lock_task_sighand(task, &flags)) {
err = -ESRCH;
goto err_task_struct;
}
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 (!lock_task_sighand(task, &flags)) {
err = -ESRCH;
goto err_task_lock;
}
if (oom_score_adj < task->signal->oom_score_adj &&
!capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
goto err_sighand;
}
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;