Hi Wensong,

0day kernel testing robot got the below dmesg.

+-------------------------------------------------------+----+
| boot_successes                                        | 26 |
| boot_failures                                         | 4  |
| BUG:unable_to_handle_kernel_NULL_pointer_dereference  | 4  |
| Oops                                                  | 4  |
| EIP_is_at_ip_vs_stop_estimator                        | 4  |
| Kernel_panic-not_syncing:Fatal_exception_in_interrupt | 4  |
| backtrace:cleanup_net                                 | 4  |
+-------------------------------------------------------+----+


[child0:2725] process_vm_readv (347) returned ENOSYS, marking as inactive.
[child0:2725] uid changed! Was: 0, now -788547075
Bailing main loop. Exit reason: UID changed.
[   12.182233] BUG: unable to handle kernel NULL pointer dereference at 00000004
[   12.183011] IP: [<4c2f6567>] ip_vs_stop_estimator+0x20/0x3e
[   12.183011] *pdpt = 0000000000000000 *pde = f000ff53f000ff53 [   12.183011] Oops: 0002 [#1] DEBUG_PAGEALLOC
[   12.183011] Modules linked in:
[   12.183011] CPU: 0 PID: 57 Comm: kworker/u2:1 Not tainted 3.15.0-rc8 #1
[   12.183011] Workqueue: netns cleanup_net
[   12.183011] task: 528773f0 ti: 52878000 task.ti: 52878000
[   12.183011] EIP: 0060:[<4c2f6567>] EFLAGS: 00010206 CPU: 0
[   12.183011] EIP is at ip_vs_stop_estimator+0x20/0x3e
[   12.183011] EAX: 00000000 EBX: 51c39a54 ECX: 00000000 EDX: 00000000
[   12.183011] ESI: 51c39bf0 EDI: 51c399cc EBP: 52879e70 ESP: 52879e68
[   12.183011]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
[   12.183011] CR0: 8005003b CR2: 00000004 CR3: 12fbe000 CR4: 000006b0
[   12.183011] DR0: 080cb000 DR1: c0100220 DR2: 00000000 DR3: 00000000
[   12.183011] DR6: ffff0ff0 DR7: 00000600
[   12.183011] Stack:
[   12.183011]  51c39800 51c3d340 52879e88 4c2f3400 51c39b14 51c3d340 4c7630bc 52879eb8
[   12.183011]  52879e94 4c2ef3b2 51c3d340 52879ea8 4c2b7509 4c7630bc 52879eb8 00000000
[   12.183011]  52879ecc 4c2b7c5b 51c3d370 51c3d370 51c3d378 51c3d378 52817b80 00000000
[   12.183011] Call Trace:
[   12.183011]  [<4c2f3400>] ip_vs_control_net_cleanup+0x8b/0x9c
[   12.183011]  [<4c2ef3b2>] __ip_vs_cleanup+0x27/0x3b
[   12.183011]  [<4c2b7509>] ops_exit_list+0x2e/0x3b
[   12.183011]  [<4c2b7c5b>] cleanup_net+0xbf/0x138
[   12.183011]  [<4be33e6a>] process_one_work+0x1c5/0x2dc
[   12.183011]  [<4be33de7>] ? process_one_work+0x142/0x2dc
[   12.183011]  [<4be348cc>] worker_thread+0x126/0x1c3
[   12.183011]  [<4be347a6>] ? rescuer_thread+0x203/0x203
[   12.183011]  [<4be37e01>] kthread+0x86/0x8b
[   12.183011]  [<4c41b380>] ret_from_kernel_thread+0x20/0x30
[   12.183011]  [<4be37d7b>] ? init_completion+0x1e/0x1e
[   12.183011] Code: e8 0b 40 12 00 5b 5b 5e 5f 5d c3 55 89 e5 56 53 8b b0 38 09 00 00 89 d3 81 c6 f0 03 00 00 89 f0 e8 f2 3d 12 00 8b 43 34 8b 53 30 <89> 42 04 89 10 89 f0 c7 43 30 00 01 10 00 c7 43 34 00 02 20 00
[   12.183011] EIP: [<4c2f6567>] ip_vs_stop_estimator+0x20/0x3e SS:ESP 0068:52879e68
[   12.183011] CR2: 0000000000000004
[   12.183011] ---[ end trace ac697d9f45d2a83f ]---
[   12.183011] Kernel panic - not syncing: Fatal exception in interrupt

git bisect  bad fad01e866afdbe01a1f3ec06a39c3a8b9e197014  # 15:45      0-      5  Linux 3.15-rc8
git bisect  bad fad01e866afdbe01a1f3ec06a39c3a8b9e197014  # 15:45      0-      5  Linux 3.15-rc8
git bisect  bad 455c6fdbd219161bd09b1165f11699d6d73de11c  # 15:50     18-      1  Linux 3.14
git bisect  bad d8ec26d7f8287f5788a494f56e8814210f0e64be  # 15:53      3-      1  Linux 3.13
git bisect  bad 5e01dc7b26d9f24f39abace5da98ccbd6a5ceb52  # 16:04     18-      1  Linux 3.12
git bisect  bad 6e4664525b1db28f8c4e1130957f70a94c19213e  # 16:10      1-      1  Linux 3.11
git bisect  bad 8bb495e3f02401ee6f76d1b1d77f3ac9f079e376  # 16:13      5-      2  Linux 3.10
git bisect  bad c1be5a5b1b355d40e6cf79cc979eb66dafa24ad1  # 16:25     37-      6  Linux 3.9
git bisect  bad 19f949f52599ba7c3f67a5897ac6be14bfcb1200  # 16:27     28-     32  Linux 3.8
git bisect  bad 29594404d7fe73cd80eaa4ee8c43dcc53970c60e  # 16:35     41-     39  Linux 3.7
git bisect  bad a0d271cbfed1dd50278c6b06bead3d00ba0a88f9  # 16:41     17-     19  Linux 3.6
git bisect  bad 28a33cbc24e4256c143dce96c7d93bf423229f92  # 16:45    149-    104  Linux 3.5
git bisect  bad 76e10d158efb6d4516018846f60c2ab5501900bc  # 16:48     20-     21  Linux 3.4
git bisect  bad c16fa4f2ad19908a47c63d8fa436a1178438c7e7  # 16:50     13-     14  Linux 3.3
git bisect  bad 805a6af8dba5dfdd35ec35dc52ec0122400b2610  # 16:53      7-      8  Linux 3.2
git bisect  bad c3b92c8787367a8bb53d57d9789b558f1295cc96  # 16:57     17-     18  Linux 3.1
git bisect  bad 02f8c6aee8df3cdc935e9bdd4f2d020306035dbe  # 17:03      2-      3  Linux 3.0


This script may reproduce the error.

-----------------------------------------------------------------------------
#!/bin/bash

kernel=$1

kvm=(
	qemu-system-x86_64 -cpu kvm64 -enable-kvm
 	-kernel $kernel
	-smp 2
	-m 256M
	-net nic,vlan=0,macaddr=00:00:00:00:00:00,model=virtio
	-net user,vlan=0
	-net nic,vlan=1,model=e1000
	-net user,vlan=1
	-boot order=nc
	-no-reboot
	-watchdog i6300esb
	-serial stdio
	-display none
	-monitor null
)

append=(
	debug
	sched_debug
	apic=debug
	ignore_loglevel
	sysrq_always_enabled
	panic=10
	prompt_ramdisk=0
	earlyprintk=ttyS0,115200
	console=ttyS0,115200
	console=tty0
	vga=normal
	root=/dev/ram0
	rw
)

"${kvm[@]}" --append "${append[*]}"
-----------------------------------------------------------------------------

Thanks,
Jet