From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f197.google.com (mail-io0-f197.google.com [209.85.223.197]) by kanga.kvack.org (Postfix) with ESMTP id 468F76B0003 for ; Wed, 7 Mar 2018 18:52:18 -0500 (EST) Received: by mail-io0-f197.google.com with SMTP id m70so3864972ioi.8 for ; Wed, 07 Mar 2018 15:52:18 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 84sor8611905ita.76.2018.03.07.15.52.16 for (Google Transport Security); Wed, 07 Mar 2018 15:52:17 -0800 (PST) Date: Wed, 7 Mar 2018 15:52:15 -0800 (PST) From: David Rientjes Subject: [patch] mm, oom: remove 3% bonus for CAP_SYS_ADMIN processes Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Gaurav Kohli , Andrew Morton Cc: mhocko@suse.com, kirill.shutemov@linux.intel.com, Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org Since the 2.6 kernel, the oom killer has slightly biased away from CAP_SYS_ADMIN processes by discounting some of its memory usage in comparison to other processes. This has always been implicit and nothing exactly relies on the behavior. Gaurav notices that __task_cred() can dereference a potentially freed pointer if the task under consideration is exiting because a reference to the task_struct is not held. Remove the CAP_SYS_ADMIN bias so that all processes are treated equally. If any CAP_SYS_ADMIN process would like to be biased against, it is always allowed to adjust /proc/pid/oom_score_adj. Reported-by: Gaurav Kohli Signed-off-by: David Rientjes --- mm/oom_kill.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -224,13 +224,6 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, mm_pgtables_bytes(p->mm) / PAGE_SIZE; task_unlock(p); - /* - * Root processes get 3% bonus, just like the __vm_enough_memory() - * implementation used by LSMs. - */ - if (has_capability_noaudit(p, CAP_SYS_ADMIN)) - points -= (points * 3) / 100; - /* Normalize to oom_score_adj units */ adj *= totalpages / 1000; points += adj;