FYI, we noticed the following commit:

commit: cc44ddf7f666875a3062daef112c8616de9bdb34 ("kernfs, sysfs, cgroup: Support fs_context")
https://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git mount-context

in testcase: trinity
with following parameters:

	runtime: 300s

test-description: Trinity is a linux system call fuzz tester.
test-url: http://codemonkey.org.uk/projects/trinity/


on test machine: qemu-system-x86_64 -enable-kvm -m 420M

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+------------------------------------------+------------+------------+
|                                          | 7f8b6dda64 | cc44ddf7f6 |
+------------------------------------------+------------+------------+
| boot_successes                           | 8          | 2          |
| boot_failures                            | 0          | 6          |
| BUG:unable_to_handle_kernel              | 0          | 6          |
| Oops:#[##]                               | 0          | 6          |
| EIP:cgroup_fs_context_free               | 0          | 6          |
| Kernel_panic-not_syncing:Fatal_exception | 0          | 6          |
+------------------------------------------+------------+------------+



[    9.571023] BUG: unable to handle kernel NULL pointer dereference at 00000044
[    9.571870] IP: cgroup_fs_context_free+0x1a/0x76
[    9.572469] *pdpt = 0000000016679001 *pde = 0000000000000000 
[    9.572471] 
[    9.573487] Oops: 0000 [#1] PREEMPT
[    9.573961] Modules linked in:
[    9.574414] CPU: 0 PID: 1 Comm: init Tainted: G S              4.12.0-rc4-00149-gcc44ddf #3
[    9.575454] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
[    9.576684] task: d903c000 task.stack: d9040000
[    9.577274] EIP: cgroup_fs_context_free+0x1a/0x76
[    9.577856] EFLAGS: 00010287 CPU: 0
[    9.578343] EAX: 00000000 EBX: 00000000 ECX: ffffffea EDX: c107a517
[    9.579066] ESI: d6653a80 EDI: d6653a80 EBP: d9041f18 ESP: d9041f10
[    9.579806]  DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068
[    9.593513] CR0: 80050033 CR2: 00000044 CR3: 19139be0 CR4: 000006f0
[    9.594245] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[    9.594971] DR6: fffe0ff0 DR7: 00000400
[    9.595490] Call Trace:
[    9.595887]  put_fs_context+0x34/0x8c
[    9.596420]  do_mount+0x815/0x839
[    9.596883]  ? _copy_from_user+0x38/0x51
[    9.597423]  ? strndup_user+0x27/0x3f
[    9.597918]  SyS_mount+0x52/0x76
[    9.598386]  do_int80_syscall_32+0x46/0x83
[    9.598915]  entry_INT80_32+0x31/0x31
[    9.599422] EIP: 0xb7681c3e
[    9.599866] EFLAGS: 00000296 CPU: 0
[    9.600369] EAX: ffffffda EBX: 0804a3a9 ECX: 0804a3a1 EDX: 0804a3a9
[    9.601105] ESI: 0000000e EDI: 00000000 EBP: bf92f008 ESP: bf92ef6c
[    9.601836]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b
[    9.602490] Code: 48 00 74 0a 55 89 e5 e8 7b 3d 00 00 5d c3 31 c0 c3 55 89 e5 56 89 c6 53 8b 40 54 e8 3e a1 04 00 8b 46 58 e8 36 a1 04 00 8b 5e 40 <f6> 43 44 01 75 39 b8 01 00 00 00 e8 af 29 fd ff 8b 43 18 a8 03
[    9.604640] EIP: cgroup_fs_context_free+0x1a/0x76 SS:ESP: 0068:d9041f10
[    9.605419] CR2: 0000000000000044
[    9.605899] ---[ end trace 8e72d62a2c66ef5a ]---


To reproduce:

        git clone https://github.com/01org/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script  # job-script is attached in this email



Thanks,
Xiaolong