From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 44D0B6B0008 for ; Mon, 6 Aug 2018 13:49:39 -0400 (EDT) Received: by mail-pf1-f197.google.com with SMTP id q21-v6so8954347pff.21 for ; Mon, 06 Aug 2018 10:49:39 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id w5-v6sor3886366pfn.0.2018.08.06.10.49.37 for (Google Transport Security); Mon, 06 Aug 2018 10:49:38 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180806174410.GB10003@dhcp22.suse.cz> References: <0000000000006350880572c61e62@google.com> <20180806174410.GB10003@dhcp22.suse.cz> From: Dmitry Vyukov Date: Mon, 6 Aug 2018 19:49:16 +0200 Message-ID: Subject: Re: WARNING in try_charge Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: syzbot , cgroups@vger.kernel.org, Johannes Weiner , LKML , Linux-MM , Tetsuo Handa , syzkaller-bugs , Vladimir Davydov On Mon, Aug 6, 2018 at 7:44 PM, Michal Hocko wrote: > On Mon 06-08-18 08:42:02, syzbot wrote: >> Hello, >> >> syzbot has tested the proposed patch but the reproducer still triggered >> crash: >> WARNING in try_charge >> >> Killed process 6410 (syz-executor5) total-vm:37708kB, anon-rss:2128kB, >> file-rss:0kB, shmem-rss:0kB >> oom_reaper: reaped process 6410 (syz-executor5), now anon-rss:0kB, >> file-rss:0kB, shmem-rss:0kB >> task=syz-executor5 pid=6410 invoked memcg oom killer. oom_victim=1 > > Thank you. This is useful. The full oom picture is this > : [ 65.363983] task=syz-executor5 pid=6415 invoked memcg oom killer. oom_victim=0 > [...] > : [ 65.920355] Task in /ile0 killed as a result of limit of /ile0 > : [ 65.926389] memory: usage 0kB, limit 0kB, failcnt 20 > : [ 65.931518] memory+swap: usage 0kB, limit 9007199254740988kB, failcnt 0 > : [ 65.938296] kmem: usage 0kB, limit 9007199254740988kB, failcnt 0 > : [ 65.944467] Memory cgroup stats for /ile0: cache:0KB rss:0KB rss_huge:0KB shmem:0KB mapped_file:0KB dirty:0KB writeback:0KB swap:0KB inactive_anon:0KB active_anon:0KB inactive_file:0KB active_file:0KB unevictable:0KB > : [ 65.963878] Tasks state (memory values in pages): > : [ 65.968743] [ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name > : [ 65.977615] [ 6410] 0 6410 9427 532 61440 0 0 syz-executor5 > : [ 65.986647] Memory cgroup out of memory: Kill process 6410 (syz-executor5) score 547000 or sacrifice child > : [ 65.996474] Killed process 6410 (syz-executor5) total-vm:37708kB, anon-rss:2128kB, file-rss:0kB, shmem-rss:0kB > : [ 66.007471] oom_reaper: reaped process 6410 (syz-executor5), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB > : [ 66.017652] task=syz-executor5 pid=6410 invoked memcg oom killer. oom_victim=1 > : [ 66.025137] ------------[ cut here ]------------ > : [ 66.029927] Memory cgroup charge failed because of no reclaimable memory! This looks like a misconfiguration or a kernel bug. > : [ 66.030061] WARNING: CPU: 1 PID: 6410 at mm/memcontrol.c:1707 try_charge+0x734/0x1680 > > So we have only a single task in the memcg and it is this task which > triggers the OOM. It gets killed and oom_reaped. This means that > out_of_memory should return with true and so we should retry and force > the charge as I've already mentioned. For some reason this task has > triggered the oom killer path again and then we haven't found any > eligible task and resulted in the warning. This shouldn't happen. > > I will stare to the code some more to see how the heck we get there > without passing > if (unlikely(tsk_is_oom_victim(current) || > fatal_signal_pending(current) || > current->flags & PF_EXITING)) > goto force; This is the syzkaller reproducer if it will give you any hints: mkdir(&(0x7f0000000340)='./file0\x00', 0x0) mount(&(0x7f00000000c0)='./file0//ile0\x00', &(0x7f0000000080)='./file0\x00', &(0x7f0000000200)='cgroup2\x00', 0x0, 0x0) r0 = open(&(0x7f0000000040)='./file0//ile0\x00', 0x0, 0x0) r1 = openat$cgroup_procs(r0, &(0x7f00000001c0)='cgroup.procs\x00', 0x2, 0x0) write$cgroup_pid(r1, &(0x7f0000000100), 0x12) syz_mount_image$xfs(&(0x7f0000000280)='xfs\x00', &(0x7f00000002c0)='./file0//ile0\x00', 0x0, 0x0, &(0x7f0000000740), 0x0, &(0x7f0000000800)) getsockopt$sock_cred(r0, 0x1, 0x11, &(0x7f0000000180), &(0x7f0000000240)=0xc) r2 = open(&(0x7f0000000040)='./file0//ile0\x00', 0x0, 0x0) write$FUSE_STATFS(r2, &(0x7f0000000280)={0x60, 0xfffffffffffffffe, 0x7, {{0x401, 0x7, 0x7d, 0x1c, 0xd8, 0xb7, 0x2, 0x3}}}, 0x60) r3 = openat$cgroup_int(r2, &(0x7f00000001c0)='memory.max\x00', 0x2, 0x0) write$cgroup_int(r3, &(0x7f00000000c0), 0x12)