Happens on my system too. I did a fresh install of Vivid daily two days ago (Feb 3), did a update/upgrade today (Feb 5), and after the reboot dmesg shows: [ 11.252422] ------------[ cut here ]------------ [ 11.252475] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.252526] invalid opcode: 0000 [#1] SMP [ 11.252564] Modules linked in: hid_generic hp_wmi sparse_keymap intel_rapl intel_soc_dts_thermal intel_powerclamp coretemp arc4 kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel cryptd rtl8723be btcoexist rtl8723_common rtl_pci rtlwifi mac80211 usbhid i915 cfg80211 snd_hda_codec_hdmi serio_raw snd_soc_rt5640 snd_soc_rl6231 snd_hda_codec_realtek snd_hda_codec_generic snd_soc_core drm_kms_helper snd_compress snd_pcm_dmaengine snd_seq_midi lpc_ich rtsx_pci_ms snd_seq_midi_event drm memstick mei_txe snd_hda_intel mei snd_rawmidi snd_hda_controller snd_hda_codec iosf_mbi snd_hwdep i2c_algo_bit snd_pcm shpchp snd_seq wmi snd_seq_device snd_timer snd video dw_dmac hp_wireless dw_dmac_core int3403_thermal int3400_thermal acpi_thermal_rel soundcore intel_smartconnect i2c_hid hid bnep rfcomm snd_soc_sst_acpi [ 11.253253] rfkill_gpio i2c_designware_platform pwm_lpss_platform i2c_designware_core parport_pc spi_pxa2xx_platform 8250_dw ppdev pwm_lpss lp parport btusb bluetooth joydev mac_hid nls_iso8859_1 mmc_block rtsx_pci_sdmmc psmouse rtsx_pci sdhci_acpi sdhci [ 11.253463] CPU: 1 PID: 868 Comm: thermald Not tainted 3.18.0-12-generic #13-Ubuntu [ 11.253521] Hardware name: Hewlett-Packard HP Stream Notebook PC 13/802A, BIOS F.05 11/28/2014 [ 11.253586] task: ffff8800772dda00 ti: ffff8800720a8000 task.ti: ffff8800720a8000 [ 11.253642] RIP: 0010:[] [] kfree+0x143/0x150 [ 11.253707] RSP: 0018:ffff8800720abe18 EFLAGS: 00010246 [ 11.253748] RAX: 01ffff0000000400 RBX: ffffffff811f075d RCX: 0000000000000ec6 [ 11.253801] RDX: 0000000000000000 RSI: ffff880076c96800 RDI: ffffffff811f075d [ 11.253854] RBP: ffff8800720abe38 R08: 0000000000016800 R09: ffffea0000047c00 [ 11.253908] R10: ffffffff8145dc27 R11: 0000000000000246 R12: 00007fff15acbae8 [ 11.253962] R13: ffffffffc03787ea R14: 0000000080087304 R15: 00007fff15acbae8 [ 11.254017] FS: 00007f9c1a78c840(0000) GS:ffff880076c80000(0000) knlGS:0000000000000000 [ 11.254078] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 11.254122] CR2: 00007f9c1a803060 CR3: 00000000797f5000 CR4: 00000000001007e0 [ 11.254176] Stack: [ 11.254193] 00007fff15acbae8 0000000000000000 00007fff15acbae8 ffff880077b702f8 [ 11.254258] ffff8800720abea8 ffffffffc03787ea ffff88003f4fe6f8 ffff88007713b020 [ 11.254322] 0000000000000000 ffff8800720abe88 0000000000000000 ffffffff811f075d [ 11.254386] Call Trace: [ 11.254426] [] acpi_thermal_rel_ioctl+0x21a/0xa30 [acpi_thermal_rel] [ 11.254495] [] ? ftrace_raw_event_do_sys_open+0x8d/0xe0 [ 11.254550] [] do_vfs_ioctl+0x2c8/0x4a0 [ 11.254595] [] ? final_putname+0x26/0x50 [ 11.254640] [] ? putname+0x29/0x40 [ 11.254681] [] ? do_sys_open+0x1b9/0x280 [ 11.254725] [] SyS_ioctl+0x81/0xa0 [ 11.254767] [] system_call_fastpath+0x16/0x1b [ 11.254814] Code: 49 8b 41 30 49 8b 11 80 e6 80 4c 0f 45 c8 e9 3b ff ff ff 0f 1f 44 00 00 4c 89 d1 48 89 da 4c 89 ce e8 32 f9 ff ff e9 71 ff ff ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 f7 c6 06 [ 11.255096] RIP [] kfree+0x143/0x150 [ 11.255142] RSP [ 11.265376] ---[ end trace fc4d3c2cb3582f3e ]--- [ 11.321998] init: thermald main process (868) killed by SEGV signal [ 11.322021] init: thermald main process ended, respawning [ 11.375126] ------------[ cut here ]------------ The error appears 11 times in dmesg, all within one second: $ dmesg | grep -A1 slub [ 11.252475] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.252526] invalid opcode: 0000 [#1] SMP -- [ 11.375178] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.375228] invalid opcode: 0000 [#2] SMP -- [ 11.515325] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.517725] invalid opcode: 0000 [#3] SMP -- [ 11.667291] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.669728] invalid opcode: 0000 [#4] SMP -- [ 11.789354] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.791802] invalid opcode: 0000 [#5] SMP -- [ 11.910164] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 11.912595] invalid opcode: 0000 [#6] SMP -- [ 12.041594] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 12.044000] invalid opcode: 0000 [#7] SMP -- [ 12.174770] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 12.177060] invalid opcode: 0000 [#8] SMP -- [ 12.292074] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 12.294512] invalid opcode: 0000 [#9] SMP -- [ 12.418418] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 12.420871] invalid opcode: 0000 [#10] SMP -- [ 12.537799] kernel BUG at /build/buildd/linux-3.18.0/mm/slub.c:3334! [ 12.540233] invalid opcode: 0000 [#11] SMP