From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757047AbdLQXRP (ORCPT ); Sun, 17 Dec 2017 18:17:15 -0500 Received: from shells.gnugeneration.com ([66.240.222.126]:60640 "EHLO shells.gnugeneration.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753008AbdLQXRO (ORCPT ); Sun, 17 Dec 2017 18:17:14 -0500 Date: Sun, 17 Dec 2017 15:24:48 -0800 From: vcaputo@pengaru.com To: Bronek Kozicki Cc: linux-kernel@vger.kernel.org, tj@kernel.org Subject: Re: PROBLEM: NULL pointer dereference in kernel 4.14.6 Message-ID: <20171217232448.yfaxxew2ijaay7iu@shells.gnugeneration.com> References: <1513512885.3653140.1207725096.395A9CCC@webmail.messagingengine.com> <08995310-d853-ee77-ed1f-26cc336a4a30@incorrekt.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <08995310-d853-ee77-ed1f-26cc336a4a30@incorrekt.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 17, 2017 at 05:49:44PM +0000, Bronek Kozicki wrote: > I just upgraded to 4.14.7 and tried to reproduce this error, this time under strace. As you can see this happens when systemctl tries to read a specific entry under /sys/fs . In case this matters, the entry is for a small virtual machine running under qemu/kvm and managed by libvirt. > > open("/sys/fs/cgroup/unified/machine.slice", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5 > fstat(5, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0 > getdents(5, /* 12 entries */, 32768) = 464 > openat(AT_FDCWD, "/sys/fs/cgroup/unified/machine.slice/machine-qemu\\x2d1\\x2dkartuzy\\x2dspice.scope/cgroup.procs", O_RDONLY|O_CLOEXEC) = 8 > fstat(8, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0 > read(8, ) = ? > +++ killed by SIGKILL +++ > [1] 12078 killed strace -- systemctl status > > This recently came through lkml, may be related: https://marc.info/?l=linux-kernel&m=151320108922415&w=2 CCd Tejun > B. > > > [ 1889.226051] ================================================================================ > [ 1889.235286] UBSAN: Undefined behaviour in kernel/cgroup/pids.c:67:9 > [ 1889.241563] member access within null pointer of type 'struct pids_cgroup' > [ 1889.249920] ================================================================================ > [ 1889.259698] BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0 > [ 1889.267524] IP: pids_free+0x28/0xb0 > [ 1889.272394] PGD 0 P4D 0 > [ 1889.274925] Oops: 0000 [#1] SMP > [ 1889.278061] Modules linked in: ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter devlink joydev hid_logitech_hidpp mxm_wmi intel_rapl sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmu > l crc32c_intel ghash_clmulni_intel pcbc aesni_intel aes_x86_64 crypto_simd glue_helper cryptd ext4 intel_cstate crc16 mbcache jbd2 fscrypto nls_iso8859_1 nls_cp437 evdev input_leds led_class vfat fat intel_rapl_perf mac_hid pcspkr hid_logitech_dj igb ptp mei_me pps_ > core i2c_i801 i2c_algo_bit mei lpc_ich ioatdma tpm_tis tpm_tis_core dca shpchp tpm wmi button sch_fq_codel sg ip_tables x_tables usbhid hid zfs(PO) zunicode(PO) zavl(PO) icp(PO) sd_mod serio_raw atkbd libps2 isci ahci libsas libahci xhci_pci ehci_pci mpt3sas xhci_hc > d ehci_hcd raid_class libata > [ 1889.349864] scsi_transport_sas usbcore scsi_mod usb_common i8042 serio zcommon(PO) znvpair(PO) spl(O) nvme nvme_core bridge stp llc vhost_net tun tap vhost vfio_pci irqbypass vfio_virqfd vfio_iommu_type1 vfio > [ 1889.368439] CPU: 1 PID: 12084 Comm: systemctl Tainted: P W O 4.14.7-1-ARCH #1 > [ 1889.376525] Hardware name: Supermicro X9DA7/E/X9DA7/E, BIOS 3.0a 07/02/2014 > [ 1889.383474] task: ffff93149aaec140 task.stack: ffffa88c3836c000 > [ 1889.389387] RIP: 0010:pids_free+0x28/0xb0 > [ 1889.393388] RSP: 0018:ffffa88c3836fcc8 EFLAGS: 00010282 > [ 1889.398605] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000006 > [ 1889.405731] RDX: 0000000000000000 RSI: 0000000000000202 RDI: 0000000000000202 > [ 1889.412854] RBP: ffff931499ab2d58 R08: 000000000000079a R09: 0000000000000000 > [ 1889.419979] R10: 00000000001f5954 R11: 000000000003d040 R12: 0000000056e21a48 > [ 1889.427102] R13: ffffffffa91de5c0 R14: ffff93247b0598c0 R15: ffffffffa91cd0a0 > [ 1889.434227] FS: 00007f18eee6b8c0(0000) GS:ffff931ebfa40000(0000) knlGS:0000000000000000 > [ 1889.442302] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 1889.448041] CR2: 00000000000000b0 CR3: 0000000611019003 CR4: 00000000001626e0 > [ 1889.455164] Call Trace: > [ 1889.457610] cgroup_free+0xaa/0x190 > [ 1889.461095] __put_task_struct+0x68/0x230 > [ 1889.465105] ? seq_printf+0x4e/0x70 > [ 1889.468591] css_task_iter_next+0x74/0x90 > [ 1889.472594] kernfs_seq_next+0x58/0x110 > [ 1889.476424] seq_read+0x36c/0x620 > [ 1889.479735] __vfs_read+0x54/0x2e0 > [ 1889.483134] vfs_read+0x9d/0x200 > [ 1889.486358] SyS_read+0x52/0xc0 > [ 1889.489494] do_syscall_64+0x69/0x1e0 > [ 1889.493152] entry_SYSCALL64_slow_path+0x25/0x25 > [ 1889.497771] RIP: 0033:0x7f18ee784a11 > [ 1889.501341] RSP: 002b:00007ffd56942618 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > [ 1889.508897] RAX: ffffffffffffffda RBX: 0000559a9ae6d260 RCX: 00007f18ee784a11 > [ 1889.516022] RDX: 0000000000001000 RSI: 0000559a9ae80f70 RDI: 0000000000000008 > [ 1889.523145] RBP: 0000000000000d68 R08: 0000000000000003 R09: ffffffffffffffb0 > [ 1889.530270] R10: 0000000000001000 R11: 0000000000000246 R12: 00007f18eea4b700 > [ 1889.537395] R13: 00007f18eea4c240 R14: 0000559a9ae6d260 R15: 0000000000000000 > [ 1889.544518] Code: 44 00 00 0f 1f 44 00 00 48 81 ff c8 f7 ff ff 55 53 48 89 fb 74 4c 48 8b 9b 38 08 00 00 48 85 db 74 7c 48 8b 5b 50 48 85 db 74 63 <48> 83 bb b0 00 00 00 00 74 2a 48 c7 c5 60 2e 1e a9 48 89 df e8 > [ 1889.563368] RIP: pids_free+0x28/0xb0 RSP: ffffa88c3836fcc8 > [ 1889.568846] CR2: 00000000000000b0 > [ 1889.572175] ---[ end trace eab2ed000b4d5c66 ]---