From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb1-f198.google.com (mail-yb1-f198.google.com [209.85.219.198]) by kanga.kvack.org (Postfix) with ESMTP id 603DB6B04AD for ; Mon, 29 Oct 2018 17:52:17 -0400 (EDT) Received: by mail-yb1-f198.google.com with SMTP id k14-v6so3488672ybd.2 for ; Mon, 29 Oct 2018 14:52:17 -0700 (PDT) Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com. [67.231.145.42]) by mx.google.com with ESMTPS id w73-v6si13218147yww.453.2018.10.29.14.52.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Oct 2018 14:52:16 -0700 (PDT) From: Roman Gushchin Subject: [PATCH] mm: handle no memcg case in memcg_kmem_charge() properly Date: Mon, 29 Oct 2018 21:51:55 +0000 Message-ID: <20181029215123.17830-1-guro@fb.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: "linux-mm@kvack.org" Cc: Mike Galbraith , "linux-kernel@vger.kernel.org" , Kernel Team , Roman Gushchin , Michal Hocko , Johannes Weiner , Vladimir Davydov , Andrew Morton Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") on a system with "cgroup_disable=3Dmemory" boot option: the system panics with the following stack trace: [0.928542] BUG: unable to handle kernel NULL pointer dereference at 00000= 000000000f8 [0.929317] PGD 0 P4D 0 [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-= 20180531_142017-buildhw-08.phx2.fed4 [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7= 00 00 00 41 56 48 89 f8 49 89 fe 49 [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: 0000000000000= 000 [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: 0000000000000= 0f8 [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: ffff99ff7cd37= a40 [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: 0000000000000= 020 [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: ffff99ff7da1e= c60 [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) knlGS:00= 00000000000000 [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: 0000000000760= ef0 [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000= 000 [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000= 400 [0.942110] PKRU: 55555554 [0.942412] Call Trace: [0.942673] try_charge+0xcb/0x780 [0.943031] memcg_kmem_charge_memcg+0x28/0x80 [0.943486] ? __vmalloc_node_range+0x1e4/0x280 [0.943971] memcg_kmem_charge+0x8b/0x1d0 [0.944396] copy_process.part.41+0x1ca/0x2070 [0.944853] ? get_acl+0x1a/0x120 [0.945200] ? shmem_tmpfile+0x90/0x90 [0.945596] _do_fork+0xd7/0x3d0 [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c [0.946421] do_syscall_64+0x5a/0x180 [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe The problem occurs because get_mem_cgroup_from_current() returns the NULL pointer if memory controller is disabled. Let's check if this is a case at the beginning of memcg_kmem_charge() and just return 0 if mem_cgroup_disabled() returns true. This is how we handle this case in many other places in the memory controller code. Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") Reported-by: Mike Galbraith Signed-off-by: Roman Gushchin Cc: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Andrew Morton --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 54920cbc46bf..6e1469b80cb7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, i= nt order) struct mem_cgroup *memcg; int ret =3D 0; =20 - if (memcg_kmem_bypass()) + if (mem_cgroup_disabled() || memcg_kmem_bypass()) return 0; =20 memcg =3D get_mem_cgroup_from_current(); --=20 2.17.2