From d46078b2888947a86b6bb997cd5927e602e8fdc9 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Thu, 5 Apr 2018 16:25:19 -0700 Subject: [PATCH] mm, oom: remove 3% bonus for CAP_SYS_ADMIN processes 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. Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1803071548510.6996@chino.kir.corp.google.com Signed-off-by: David Rientjes Reported-by: Gaurav Kohli Acked-by: Michal Hocko Cc: Kirill A. Shutemov Cc: Andrea Arcangeli Cc: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 82a92ad67af3..c4c9ecd17c6e 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -226,13 +226,6 @@ 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; -- 2.30.2