From: Michal Hocko <mhocko@kernel.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, David Rientjes <rientjes@google.com>, linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>, Michal Hocko <mhocko@suse.com> Subject: [PATCH] mm, oom_reaper: do not use siglock in try_oom_reaper Date: Tue, 31 May 2016 09:23:43 +0200 Message-ID: <1464679423-30218-1-git-send-email-mhocko@kernel.org> (raw) From: Michal Hocko <mhocko@suse.com> Oleg has noted that siglock usage in try_oom_reaper is both pointless and dangerous. signal_group_exit can be checked lockless. The problem is that sighand becomes NULL in __exit_signal so we can crash. Fixes: 3ef22dfff239 ("oom, oom_reaper: try to reap tasks which skip regular OOM killer path") Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Michal Hocko <mhocko@suse.com> --- Hi Andrew, Oleg has noticed this while reviewing http://lkml.kernel.org/r/20160530173505.GA25287@redhat.com this should go in 4.7. mm/oom_kill.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index e01cc3e2e755..25eac62c190c 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -625,8 +625,6 @@ void try_oom_reaper(struct task_struct *tsk) if (atomic_read(&mm->mm_users) > 1) { rcu_read_lock(); for_each_process(p) { - bool exiting; - if (!process_shares_mm(p, mm)) continue; if (fatal_signal_pending(p)) @@ -636,10 +634,7 @@ void try_oom_reaper(struct task_struct *tsk) * If the task is exiting make sure the whole thread group * is exiting and cannot acces mm anymore. */ - spin_lock_irq(&p->sighand->siglock); - exiting = signal_group_exit(p->signal); - spin_unlock_irq(&p->sighand->siglock); - if (exiting) + if (signal_group_exit(p->signal)) continue; /* Give up */ -- 2.8.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next reply index Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-05-31 7:23 Michal Hocko [this message] 2016-05-31 21:25 ` Oleg Nesterov
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