On 2018/09/06 20:23, Michal Hocko wrote: > On Thu 06-09-18 19:58:25, Tetsuo Handa wrote: > [...] >> >From 18876f287dd69a7c33f65c91cfcda3564233f55e Mon Sep 17 00:00:00 2001 >> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> >> Date: Thu, 6 Sep 2018 19:53:18 +0900 >> Subject: [PATCH] mm, oom: Introduce time limit for dump_tasks duration. >> >> Since printk() is slow, printing one line takes nearly 0.01 second. >> As a result, syzbot is stalling for 52 seconds trying to dump 5600 >> tasks at for_each_process() under RCU. Since such situation is almost >> inflight fork bomb attack (the OOM killer will print similar tasks for >> so many times), it makes little sense to print all candidate tasks. >> Thus, this patch introduces 3 seconds limit for printing. >> >> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> >> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > You really love timeout based solutions with randomly chosen timeouts, > don't you. This is just ugly as hell. We already have means to disable > tasks dumping (see /proc/sys/vm/oom_dump_tasks). I know /proc/sys/vm/oom_dump_tasks . Showing some entries while not always printing all entries might be helpful. For example, allow /proc/sys/vm/oom_dump_tasks > 1 and use it as timeout in seconds.
