From: Andrew Morton <akpm@linux-foundation.org>
To: vincent.guittot@linaro.org, tglx@linutronix.de,
stable@vger.kernel.org, rostedt@goodmis.org, rientjes@google.com,
peterz@infradead.org, mingo@redhat.com, mhocko@suse.com,
mgorman@suse.de, longman@redhat.com, juri.lelli@redhat.com,
jsavitz@redhat.com, herton@redhat.com, dvhart@infradead.org,
dietmar.eggemann@arm.com, dave@stgolabs.net, bsegall@google.com,
bristot@redhat.com, aquini@redhat.com, aarcange@redhat.com,
npache@redhat.com, akpm@linux-foundation.org,
patches@lists.linux.dev, linux-mm@kvack.org,
mm-commits@vger.kernel.org, torvalds@linux-foundation.org,
akpm@linux-foundation.org
Subject: [patch 10/13] oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup
Date: Thu, 21 Apr 2022 16:36:01 -0700 [thread overview]
Message-ID: <20220421233601.E2D31C385A5@smtp.kernel.org> (raw)
In-Reply-To: <20220421163508.66028a9ac2d9fb6ea05b1342@linux-foundation.org>
From: Nico Pache <npache@redhat.com>
Subject: oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup
The pthread struct is allocated on PRIVATE|ANONYMOUS memory [1] which can
be targeted by the oom reaper. This mapping is used to store the futex
robust list head; the kernel does not keep a copy of the robust list and
instead references a userspace address to maintain the robustness during a
process death. A race can occur between exit_mm and the oom reaper that
allows the oom reaper to free the memory of the futex robust list before
the exit path has handled the futex death:
CPU1 CPU2
------------------------------------------------------------------------
page_fault
do_exit "signal"
wake_oom_reaper
oom_reaper
oom_reap_task_mm (invalidates mm)
exit_mm
exit_mm_release
futex_exit_release
futex_cleanup
exit_robust_list
get_user (EFAULT- can't access memory)
If the get_user EFAULT's, the kernel will be unable to recover the waiters
on the robust_list, leaving userspace mutexes hung indefinitely.
Delay the OOM reaper, allowing more time for the exit path to perform the
futex cleanup.
Reproducer: https://gitlab.com/jsavitz/oom_futex_reproducer
Based on a patch by Michal Hocko.
[1] https://elixir.bootlin.com/glibc/glibc-2.35/source/nptl/allocatestack.c#L370
Link: https://lkml.kernel.org/r/20220414144042.677008-1-npache@redhat.com
Fixes: 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Co-developed-by: Joel Savitz <jsavitz@redhat.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Herton R. Krzesinski <herton@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joel Savitz <jsavitz@redhat.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/sched.h | 1
mm/oom_kill.c | 54 +++++++++++++++++++++++++++++-----------
2 files changed, 41 insertions(+), 14 deletions(-)
--- a/include/linux/sched.h~oom_killc-futex-delay-the-oom-reaper-to-allow-time-for-proper-futex-cleanup
+++ a/include/linux/sched.h
@@ -1443,6 +1443,7 @@ struct task_struct {
int pagefault_disabled;
#ifdef CONFIG_MMU
struct task_struct *oom_reaper_list;
+ struct timer_list oom_reaper_timer;
#endif
#ifdef CONFIG_VMAP_STACK
struct vm_struct *stack_vm_area;
--- a/mm/oom_kill.c~oom_killc-futex-delay-the-oom-reaper-to-allow-time-for-proper-futex-cleanup
+++ a/mm/oom_kill.c
@@ -632,7 +632,7 @@ done:
*/
set_bit(MMF_OOM_SKIP, &mm->flags);
- /* Drop a reference taken by wake_oom_reaper */
+ /* Drop a reference taken by queue_oom_reaper */
put_task_struct(tsk);
}
@@ -644,12 +644,12 @@ static int oom_reaper(void *unused)
struct task_struct *tsk = NULL;
wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
- spin_lock(&oom_reaper_lock);
+ spin_lock_irq(&oom_reaper_lock);
if (oom_reaper_list != NULL) {
tsk = oom_reaper_list;
oom_reaper_list = tsk->oom_reaper_list;
}
- spin_unlock(&oom_reaper_lock);
+ spin_unlock_irq(&oom_reaper_lock);
if (tsk)
oom_reap_task(tsk);
@@ -658,22 +658,48 @@ static int oom_reaper(void *unused)
return 0;
}
-static void wake_oom_reaper(struct task_struct *tsk)
+static void wake_oom_reaper(struct timer_list *timer)
{
- /* mm is already queued? */
- if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
+ struct task_struct *tsk = container_of(timer, struct task_struct,
+ oom_reaper_timer);
+ struct mm_struct *mm = tsk->signal->oom_mm;
+ unsigned long flags;
+
+ /* The victim managed to terminate on its own - see exit_mmap */
+ if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
+ put_task_struct(tsk);
return;
+ }
- get_task_struct(tsk);
-
- spin_lock(&oom_reaper_lock);
+ spin_lock_irqsave(&oom_reaper_lock, flags);
tsk->oom_reaper_list = oom_reaper_list;
oom_reaper_list = tsk;
- spin_unlock(&oom_reaper_lock);
+ spin_unlock_irqrestore(&oom_reaper_lock, flags);
trace_wake_reaper(tsk->pid);
wake_up(&oom_reaper_wait);
}
+/*
+ * Give the OOM victim time to exit naturally before invoking the oom_reaping.
+ * The timers timeout is arbitrary... the longer it is, the longer the worst
+ * case scenario for the OOM can take. If it is too small, the oom_reaper can
+ * get in the way and release resources needed by the process exit path.
+ * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
+ * before the exit path is able to wake the futex waiters.
+ */
+#define OOM_REAPER_DELAY (2*HZ)
+static void queue_oom_reaper(struct task_struct *tsk)
+{
+ /* mm is already queued? */
+ if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
+ return;
+
+ get_task_struct(tsk);
+ timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
+ tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
+ add_timer(&tsk->oom_reaper_timer);
+}
+
static int __init oom_init(void)
{
oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
@@ -681,7 +707,7 @@ static int __init oom_init(void)
}
subsys_initcall(oom_init)
#else
-static inline void wake_oom_reaper(struct task_struct *tsk)
+static inline void queue_oom_reaper(struct task_struct *tsk)
{
}
#endif /* CONFIG_MMU */
@@ -932,7 +958,7 @@ static void __oom_kill_process(struct ta
rcu_read_unlock();
if (can_oom_reap)
- wake_oom_reaper(victim);
+ queue_oom_reaper(victim);
mmdrop(mm);
put_task_struct(victim);
@@ -968,7 +994,7 @@ static void oom_kill_process(struct oom_
task_lock(victim);
if (task_will_free_mem(victim)) {
mark_oom_victim(victim);
- wake_oom_reaper(victim);
+ queue_oom_reaper(victim);
task_unlock(victim);
put_task_struct(victim);
return;
@@ -1067,7 +1093,7 @@ bool out_of_memory(struct oom_control *o
*/
if (task_will_free_mem(current)) {
mark_oom_victim(current);
- wake_oom_reaper(current);
+ queue_oom_reaper(current);
return true;
}
_
next prev parent reply other threads:[~2022-04-21 23:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-21 23:35 incoming Andrew Morton
2022-04-21 23:35 ` [patch 01/13] mm/hwpoison: fix race between hugetlb free/demotion and memory_failure_hugetlb() Andrew Morton
2022-04-21 23:35 ` [patch 02/13] mm/memory-failure.c: skip huge_zero_page in memory_failure() Andrew Morton
2022-04-21 23:35 ` [patch 03/13] memcg: sync flush only if periodic flush is delayed Andrew Morton
2022-04-21 23:35 ` [patch 04/13] userfaultfd: mark uffd_wp regardless of VM_WRITE flag Andrew Morton
2022-04-21 23:35 ` [patch 05/13] mm, hugetlb: allow for "high" userspace addresses Andrew Morton
2022-04-21 23:35 ` [patch 06/13] selftest/vm: verify mmap addr in mremap_test Andrew Morton
2022-04-21 23:35 ` [patch 07/13] selftest/vm: verify remap destination address " Andrew Morton
2022-04-21 23:35 ` [patch 08/13] selftest/vm: support xfail " Andrew Morton
2022-04-21 23:35 ` [patch 09/13] selftest/vm: add skip support to mremap_test Andrew Morton
2022-04-21 23:36 ` Andrew Morton [this message]
2022-04-21 23:36 ` [patch 11/13] MAINTAINERS: add Vincenzo Frascino to KASAN reviewers Andrew Morton
2022-04-21 23:36 ` [patch 12/13] kcov: don't generate a warning on vm_insert_page()'s failure Andrew Morton
2022-04-21 23:36 ` [patch 13/13] mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() Andrew Morton
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