In a Ubuntu-Precise server (3.2.0-27 kernel) i have this kernel panic in dmesg: [ 131.459333] ------------[ cut here ]------------ [ 131.459344] WARNING: at /build/buildd/linux-3.2.0/mm/slub.c:3374 ksize+0xb5/0xc0() [ 131.459347] Hardware name: ProLiant ML350 G6 [ 131.459349] Modules linked in: ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp iptable_filter ip_tables x_tables bridge stp xen_gntdev xen_netback xen_blkback xen_evtchn xenfs microcode usbhid hid usb_storage uas xfs radeon ttm drm_kms_helper drm ipmi_si ipmi_msghandler i2c_algo_bit psmouse i7core_edac bonding edac_core hpilo serio_raw shpchp acpi_power_meter mac_hid lp parport tg3 hpsa [ 131.459394] Pid: 1649, comm: sh Not tainted 3.2.0-27-generic #43-Ubuntu [ 131.459396] Call Trace: [ 131.459404] [] warn_slowpath_common+0x7f/0xc0 [ 131.459410] [] ? _raw_spin_unlock_irqrestore+0x1e/0x30 [ 131.459414] [] warn_slowpath_null+0x1a/0x20 [ 131.459418] [] ksize+0xb5/0xc0 [ 131.459423] [] kzfree+0x1c/0x40 [ 131.459428] [] apparmor_file_free_security+0x1a/0x20 [ 131.459434] [] security_file_free+0x16/0x20 [ 131.459439] [] __fput+0xc6/0x210 [ 131.459442] [] fput+0x25/0x30 [ 131.459446] [] filp_close+0x66/0x90 [ 131.459450] [] put_files_struct.part.10+0x7a/0xe0 [ 131.459455] [] put_files_struct+0x18/0x20 [ 131.459459] [] exit_files+0x54/0x70 [ 131.459463] [] do_exit+0x195/0x420 [ 131.459467] [] do_group_exit+0x44/0xa0 [ 131.459470] [] sys_exit_group+0x17/0x20 [ 131.459475] [] system_call_fastpath+0x16/0x1b [ 131.459478] ---[ end trace 92e87a495e3a2e5a ]--- [ 131.459487] ------------[ cut here ]------------ [ 131.459564] kernel BUG at /build/buildd/linux-3.2.0/mm/slub.c:3430! [ 131.459660] invalid opcode: 0000 [#1] SMP [ 131.459738] CPU 5 [ 131.459771] Modules linked in: ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp iptable_filter ip_tables x_tables bridge stp xen_gntdev xen_netback xen_blkback xen_evtchn xenfs microcode usbhid hid usb_storage uas xfs radeon ttm drm_kms_helper drm ipmi_si ipmi_msghandler i2c_algo_bit psmouse i7core_edac bonding edac_core hpilo serio_raw shpchp acpi_power_meter mac_hid lp parport tg3 hpsa [ 131.460775] [ 131.460802] Pid: 1649, comm: sh Tainted: G W 3.2.0-27-generic #43-Ubuntu HP ProLiant ML350 G6 [ 131.460996] RIP: e030:[] [] kfree+0x135/0x140 [ 131.461121] RSP: e02b:ffff88003126dd48 EFLAGS: 00010246 [ 131.461203] RAX: 0000000000000000 RBX: ffff880000000000 RCX: 0000000000000000 [ 131.461311] RDX: ffffffff7fffffff RSI: 0000000000000000 RDI: ffff880000000000 [ 131.465056] RBP: ffff88003126dd78 R08: ffffea0000000000 R09: ffff880000000000 [ 131.468879] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000008 [ 131.472689] R13: ffff88002b8a10c0 R14: ffffffff811329d1 R15: ffff88002b8793b0 [ 131.476640] FS: 00007f925fdfc700(0000) GS:ffff88003eea0000(0000) knlGS:0000000000000000 [ 131.480675] CS: e033 DS: 0000 ES: 0000 CR0: 000000008005003b [ 131.484618] CR2: 000000000061cd64 CR3: 0000000001c05000 CR4: 0000000000002660 [ 131.488548] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 131.492424] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 131.496321] Process sh (pid: 1649, threadinfo ffff88003126c000, task ffff8800036716f0) [ 131.500220] Stack: [ 131.504003] ffff88003126dd58 ffff880000000000 0000000000000008 ffff88002b8a10c0 [ 131.507940] ffff88002b8793b0 ffff88002b8793b0 ffff88003126dd98 ffffffff811329d1 [ 131.511852] 0000000000000008 ffff88002f4e4800 ffff88003126dda8 ffffffff812d6b9a [ 131.515843] Call Trace: [ 131.519679] [] kzfree+0x31/0x40 [ 131.523506] [] apparmor_file_free_security+0x1a/0x20 [ 131.527416] [] security_file_free+0x16/0x20 [ 131.527420] [] __fput+0xc6/0x210 [ 131.527423] [] fput+0x25/0x30 [ 131.527428] [] filp_close+0x66/0x90 [ 131.527432] [] put_files_struct.part.10+0x7a/0xe0 [ 131.527436] [] put_files_struct+0x18/0x20 [ 131.527439] [] exit_files+0x54/0x70 [ 131.527443] [] do_exit+0x195/0x420 [ 131.527446] [] do_group_exit+0x44/0xa0 [ 131.527450] [] sys_exit_group+0x17/0x20 [ 131.527454] [] system_call_fastpath+0x16/0x1b [ 131.527456] Code: 89 da 4c 89 c6 e8 d6 34 4e 00 eb 94 49 f7 00 00 c0 00 00 74 16 4c 89 c7 e8 39 17 fc ff e9 7e ff ff ff 4d 8b 40 30 e9 27 ff ff ff <0f> 0b 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 53 48 83 ec 08 66 [ 131.527481] RIP [] kfree+0x135/0x140 [ 131.527486] RSP [ 131.527513] ---[ end trace 92e87a495e3a2e5b ]--- [ 131.527515] Fixing recursive fault but reboot is needed! Hardware is a HP Proliant G5 with Ubuntu Server. setting a grub-kernel parameters "acpi=off noapic" fix this issue.