kernel BUG in ppp_generic.c, high load average after that

[Timur Irmatov]

On a server machine that runs a pppoe server I have noticed a high load average on a idle machine (CPU is 90% idle). Looking at kernel logs I have found following:

 ------------[ cut here ]------------
 kernel BUG at /build/linux-lts-wily-Ejb_ce/linux-lts-wily-4.2.0/drivers/net/ppp/ppp_generic.c:291!
 invalid opcode: 0000 [#1] SMP
 Modules linked in: btrfs xor raid6_pq ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c act_mirred sch_ingress cls_fw cls_u32 sch
iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat xt_CT nf_conntrack iptable_raw ipt_REJECT nf_reject_ipv4 xt_tcpudp iptab
p llc ebtable_filter ebtables x_tables ppdev kvm_intel kvm crct10dif_pclmul crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper
pvpanic lp 8250_fintek parport_pc parport cirrus ttm drm_kms_helper mac_hid drm syscopyarea sysfillrect sysimgblt i2c_piix4 psmouse flop

 CPU: 0 PID: 1667 Comm: pppd Not tainted 4.2.0-42-generic #49~14.04.1-Ubuntu
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 task: ffff8800660a3700 ti: ffff88002f36c000 task.ti: ffff88002f36c000
 RIP: 0010:[<ffffffff817bdbc9>] [<ffffffff817bdbc9>] ppp_pernet.part.16+0x4/0x6
 RSP: 0018:ffff88002f36fdf8 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: 000000004004743a RCX: 000000000065b528
 RDX: 00000000000001c3 RSI: 000000004004743a RDI: ffffffff81cdd580
 RBP: ffff88002f36fdf8 R08: 0000000000000000 R09: 00000000020c84e0
 R10: 00007ffcefbbf610 R11: 0000000000000246 R12: ffff880021176900
 R13: ffff880021176500 R14: 000000000065b528 R15: 000000000065b528
 FS: 00007fb63fc07740(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f5bbfeb5000 CR3: 0000000069b49000 CR4: 00000000001406f0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Stack:
  ffff88002f36fe78 ffffffff8159e7fa ffffffff81cede80 ffffffff000001c3
  ffff880036567ca8 00000000000001c3 8080808080808080 0000000000000000
  00000000fffffe00 ffffffff8120b324 0000000000000001 ffff880021176500
 Call Trace:
  [<ffffffff8159e7fa>] ppp_ioctl+0xdca/0xde0
  [<ffffffff8120b324>] ? __fd_install+0x24/0xc0
  [<ffffffff8120116d>] do_vfs_ioctl+0x2cd/0x4b0
  [<ffffffff811fd12f>] ? putname+0x5f/0x70
  [<ffffffff810c0f71>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20
  [<ffffffff812013c9>] SyS_ioctl+0x79/0x90
  [<ffffffff817c36f2>] entry_SYSCALL_64_fastpath+0x16/0x75
 Code: 00 00 00 48 c7 c7 58 9a a9 81 48 89 e5 e8 b0 be 8b ff 5d c6 05 97 97 54 00 01 c3 55 48 89 e5 0f 0b 55 48 89 e5 0f 0b 55 48 89 e5 <0f> 0b 55 48 89 e5 0f 0b 0f 1f 44 00 00 55 48 c7 c7 20 d7 cd 81
 RIP [<ffffffff817bdbc9>] ppp_pernet.part.16+0x4/0x6
  RSP <ffff88002f36fdf8>
 ---[ end trace e5e2f1c7519e1d6c ]---

Except from unusually high load average I have noticed no other problems. But some services on a machine do monitor load average and shut down if it goes too high, so I had to reboot a machine to fix the issue.

I'll be happy to give any additional information required to fix this bug.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-headers-4.2.0-42 4.2.0-42.49~14.04.1
ProcVersionSignature: Ubuntu 4.2.0-42.49~14.04.1-generic 4.2.8-ckt12
Uname: Linux 4.2.0-42-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
Date: Thu Aug 25 12:19:02 2016
InstallationDate: Installed on 2012-07-25 (1491 days ago)
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
PackageArchitecture: all
SourcePackage: linux-lts-wily
UpgradeStatus: Upgraded to trusty on 2013-04-10 (1233 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[petro (petro-petrovich)]

Same bug.

Dec 27 15:18:09 nas230 kernel: [9182662.709741] ------------[ cut here ]------------
Dec 27 15:18:09 nas230 kernel: [9182662.709896] kernel BUG at /build/linux-lts-wily-JUyKGw/linux-lts-wily-4.2.0/drivers/net/ppp/ppp_generic.c:291!
Dec 27 15:18:09 nas230 kernel: [9182662.710222] invalid opcode: 0000 [#1] SMP
Dec 27 15:18:09 nas230 kernel: [9182662.710371] Modules linked in: iptable_filter ip_tables x_tables arc4 ppp_mppe act_police cls_u32 sch_ingress sch_tbf cls_flow sch_htb ifb pppoe pppox ipmi_ssif ipmi_dev
intf ics932s401 x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd cdc_ether sb_edac usbnet mii ed
ac_core lpc_ich ioatdma nls_iso8859_1 8021q garp mrp ipmi_si stp llc 8250_fintek ipmi_msghandler wmi shpchp mac_hid bonding lp parport igb i2c_algo_bit dca ptp megaraid_sas pps_core
Dec 27 15:18:09 nas230 kernel: [9182662.712151] CPU: 7 PID: 9053 Comm: accel-pppd Not tainted 4.2.0-36-generic #42~14.04.1-Ubuntu
Dec 27 15:18:09 nas230 kernel: [9182662.712419] Hardware name: IBM IBM System x3550 M4 Server -[7914G3G]-/00AM544, BIOS -[D7E134FUS-1.51]- 10/02/2013
Dec 27 15:18:09 nas230 kernel: [9182662.712748] task: ffff88007d0cd280 ti: ffff8800361ec000 task.ti: ffff8800361ec000
Dec 27 15:18:09 nas230 kernel: [9182662.712984] RIP: 0010:[<ffffffff817bda34>] [<ffffffff817bda34>] ppp_pernet.part.16+0x4/0x6
Dec 27 15:18:09 nas230 kernel: [9182662.713257] RSP: 0018:ffff8800361efdf8 EFLAGS: 00010246
Dec 27 15:18:09 nas230 kernel: [9182662.713435] RAX: 0000000000000000 RBX: 000000004004743a RCX: 00007f201819f6a0
Dec 27 15:18:09 nas230 kernel: [9182662.713670] RDX: 00000000000001eb RSI: 000000004004743a RDI: ffffffff81cdc4a0
Dec 27 15:18:09 nas230 kernel: [9182662.713904] RBP: ffff8800361efdf8 R08: 0000000000000001 R09: ffff88026d4b9e40
Dec 27 15:18:09 nas230 kernel: [9182662.714139] R10: 0000000000004628 R11: ffff88007b92db38 R12: ffff88007b92cc00
Dec 27 15:18:09 nas230 kernel: [9182662.714374] R13: ffff88007b92db00 R14: 00007f201819f6a0 R15: 00007f201819f6a0
Dec 27 15:18:09 nas230 kernel: [9182662.714613] FS: 00007f202702b700(0000) GS:ffff880277bc0000(0000) knlGS:0000000000000000
Dec 27 15:18:09 nas230 kernel: [9182662.714878] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Dec 27 15:18:09 nas230 kernel: [9182662.715066] CR2: 00007f0ecbe964a0 CR3: 000000026d7bc000 CR4: 00000000001406e0
Dec 27 15:18:09 nas230 kernel: [9182662.715298] Stack:
Dec 27 15:18:09 nas230 kernel: [9182662.715367] ffff8800361efe78 ffffffff8159eb9a ffff880277312c60 ffff880277bd6640
Dec 27 15:18:09 nas230 kernel: [9182662.715625] ffff880277bd6640 00000000000001eb ffff88007d0cd2e8 0000000000000007
Dec 27 15:18:09 nas230 kernel: [9182662.715882] ffff8800361efeb8 ffffffff810b45bf ffff8800361efe88 ffff88007b92db00
Dec 27 15:18:09 nas230 kernel: [9182662.716139] Call Trace:
Dec 27 15:18:09 nas230 kernel: [9182662.716223] [<ffffffff8159eb9a>] ppp_ioctl+0xdca/0xde0
Dec 27 15:18:09 nas230 kernel: [9182662.716395] [<ffffffff810b45bf>] ? pick_next_task_fair+0x53f/0x8a0
Dec 27 15:18:09 nas230 kernel: [9182662.716601] [<ffffffff8120155d>] do_vfs_ioctl+0x2cd/0x4b0
De...