Mimi,

Although this occurs in the xen tree head, it's more likely related to
ima_inode_post_setattr().

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git devel/for-linus-3.8
head:   d01b193de1a961e028ee6df5ad0b34c3e56a995f
commit: d01b193de1a961e028ee6df5ad0b34c3e56a995f [0/0] xen/acpi: Support ACPI hotplug of CPUs.

[  115.499469] Write protecting the kernel read-only data: 2752k
[  134.707390] ------------[ cut here ]------------
[  134.707390] kernel BUG at /c/kernel-tests/src/linux/mm/slub.c:3479!
[  134.707390] invalid opcode: 0000 [#1] 
[  134.707390] Pid: 1, comm: init Not tainted 3.6.0-00451-gd01b193 #2 Bochs Bochs
[  134.707390] EIP: 0060:[<c1235dbe>] EFLAGS: 00000246 CPU: 0
[  134.707390] EIP is at kfree+0x2be/0x490
[  134.707390] EAX: 00000001 EBX: 00000001 ECX: 00000000 EDX: 00000000
[  134.707390] ESI: cdeef760 EDI: cd83bdac EBP: cd83bd70 ESP: cd83bd50
[  134.707390]  DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068
[  134.707390] CR0: 80050033 CR2: b7782000 CR3: 0f9a8000 CR4: 00000690
[  134.707390] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[  134.707390] DR6: 00000000 DR7: 00000000
[  134.707390] Process init (pid: 1, ti=cd83a000 task=cd838000 task.ti=cd83a000)
[  134.707390] Stack:
[  134.707390]  00000000 cd83bd5c c1085b74 cd83bd88 c1298a5e cd83a000 ffffffc3 cd83bd90
[  134.707390]  cd83bd88 c1298a5e cd83bd90 c1ffdf63 00000001 cd832914 cd83bd98 c1298d4a
[  134.707390]  00000000 00000002 cd83bdac c11e0400 c995c980 cd832914 00000000 cd83bdc4
[  134.707390] Call Trace:
[  134.707390]  [<c1085b74>] ? irq_exit+0x74/0x180
[  134.707390]  [<c1298a5e>] ? __simple_xattr_set+0x28e/0x360
[  134.707390]  [<c1298a5e>] __simple_xattr_set+0x28e/0x360
[  134.707390]  [<c1298d4a>] simple_xattr_remove+0x2a/0x40
[  134.707390]  [<c11e0400>] shmem_removexattr+0xc0/0x120
[  134.707390]  [<c14f11ed>] ima_inode_post_setattr+0x21d/0x250
[  134.707390]  [<c1284316>] notify_change+0xb66/0xc40
[  134.707390]  [<c1239c58>] do_truncate+0xf8/0x160
[  134.707390]  [<c1261fcd>] do_last.isra.38+0xb3d/0x1a80
[  134.707390]  [<c12632e1>] path_openat+0x3d1/0xd10
[  134.707390]  [<c11476cb>] ? note_interrupt+0x4db/0x7f0
[  134.707390]  [<c1263c57>] do_filp_open+0x37/0x140
[  134.707390]  [<c123ce71>] do_sys_open+0x471/0x630
[  134.707390]  [<c10881b6>] ? __find_resource+0x166/0x470
[  134.707390]  [<c123d06b>] sys_open+0x3b/0x70
[  134.707390]  [<c1de6ce1>] sysenter_do_call+0x12/0x2c
[  134.707390] Code: 89 d0 f3 ff 8b 04 9d 8c a0 2c c2 83 c0 01 85 db 89 04 9d 8c a0 2c c2 0f 84 6a 01 00 00 83 05 a8 4b 61 c2 01 83 15 ac 4b 61 c2 00 <0f> 0b 83 05 b8 4b 61 c2 01 83 15 bc 4b 61 c2 00 83 05 30 4c 61
[  134.707390] EIP: [<c1235dbe>] kfree+0x2be/0x490 SS:ESP 0068:cd83bd50

Thanks,
Fengguang