[arp] 4591591ab7: RIP:neigh_probe

Greeting,

FYI, we noticed the following commit (built with gcc-9):

commit: 4591591ab715a4e480d58a726527f2cd252f3eb1 ("arp: Remove the arp_hh_ops structure")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git Yejune-Deng/arp-Remove-the-arp_hh_ops-structure/20210220-123704


in testcase: locktorture
version: 
with following parameters:

	runtime: 300s
	test: cpuhotplug

test-description: This torture test consists of creating a number of kernel threads which acquire the lock and hold it for specific amount of time, thus simulating different critical region behaviors.
test-url: https://www.kernel.org/doc/Documentation/locking/locktorture.txt


on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 8G

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


+-------------------------------------------------------+------------+------------+
|                                                       | 38b5133ad6 | 4591591ab7 |
+-------------------------------------------------------+------------+------------+
| boot_successes                                        | 12         | 0          |
| boot_failures                                         | 0          | 12         |
| BUG:kernel_NULL_pointer_dereference,address           | 0          | 11         |
| Oops:#[##]                                            | 0          | 12         |
| RIP:neigh_probe                                       | 0          | 12         |
| Kernel_panic-not_syncing:Fatal_exception_in_interrupt | 0          | 12         |
+-------------------------------------------------------+------------+------------+


If you fix the issue, kindly add following tag
Reported-by: kernel test robot <redacted>



[  OK  ] Reached target System Time Synchronized.
[  OK  ] Reached target System Initialization.
8.973653] #PF: supervisor read access in kernel mode
[    8.975027] #PF: error_code(0x0000) - not-present page
[    8.976310] PGD 0 P4D 0
[    8.977036] Oops: 0000 [#1] SMP PTI
[    8.977973] CPU: 1 PID: 210 Comm: sd-resolve Not tainted 5.11.0-rc7-02046-g4591591ab715 #1
[    8.979998] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
[    8.981996] RIP: 0010:neigh_probe (kbuild/src/consumer/net/core/neighbour.c:1009) 
[ 8.983081] Code: 43 38 48 39 c7 74 0f be 20 0a 00 00 e8 ba d4 fd ff 48 89 c5 eb 02 31 ed c6 43 28 00 48 8b 83 50 01 00 00 65 ff 0d 81 85 87 7d <48> 8b 40 08 48 85 c0 74 0b 48 89 ee 48 89 df e8 ad 43 46 00 f0 ff
All code
========
   0:	43 38 48 39          	rex.XB cmp %cl,0x39(%r8)
   4:	c7                   	(bad)  
   5:	74 0f                	je     0x16
   7:	be 20 0a 00 00       	mov    $0xa20,%esi
   c:	e8 ba d4 fd ff       	callq  0xfffffffffffdd4cb
  11:	48 89 c5             	mov    %rax,%rbp
  14:	eb 02                	jmp    0x18
  16:	31 ed                	xor    %ebp,%ebp
  18:	c6 43 28 00          	movb   $0x0,0x28(%rbx)
  1c:	48 8b 83 50 01 00 00 	mov    0x150(%rbx),%rax
  23:	65 ff 0d 81 85 87 7d 	decl   %gs:0x7d878581(%rip)        # 0x7d8785ab
  2a:*	48 8b 40 08          	mov    0x8(%rax),%rax		<-- trapping instruction
  2e:	48 85 c0             	test   %rax,%rax
  31:	74 0b                	je     0x3e
  33:	48 89 ee             	mov    %rbp,%rsi
  36:	48 89 df             	mov    %rbx,%rdi
  39:	e8 ad 43 46 00       	callq  0x4643eb
  3e:	f0                   	lock
  3f:	ff                   	.byte 0xff

Code starting with the faulting instruction
===========================================
   0:	48 8b 40 08          	mov    0x8(%rax),%rax
   4:	48 85 c0             	test   %rax,%rax
   7:	74 0b                	je     0x14
   9:	48 89 ee             	mov    %rbp,%rsi
   c:	48 89 df             	mov    %rbx,%rdi
   f:	e8 ad 43 46 00       	callq  0x4643c1
  14:	f0                   	lock
  15:	ff                   	.byte 0xff
[    8.987379] RSP: 0018:ffff9ef6806078f0 EFLAGS: 00010286
[    8.988690] RAX: 0000000000000000 RBX: ffff8913462b6c00 RCX: 0000000000000000
[    8.990407] RDX: 0000000000000000 RSI: ffff891346125800 RDI: ffff891346125600
[    8.992143] RBP: ffff891346125600 R08: 0000000000000100 R09: ffffffff83980870
[    8.993682] R10: ffff8913468ee818 R11: 0000000000000002 R12: 0000000000000001
[    8.995282] R13: ffff891346125800 R14: ffff891346835e70 R15: 000000000000002f
[    8.996959] FS:  00007f354281f700(0000) GS:ffff8913ffd00000(0000) knlGS:0000000000000000
[    8.998964] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    9.000365] CR2: 0000000000000008 CR3: 000000013630c000 CR4: 00000000000406e0
[    9.002077] Call Trace:
[    9.002823] __neigh_event_send (kbuild/src/consumer/net/core/neighbour.c:1171) 
[    9.003849] neigh_resolve_output (kbuild/src/consumer/net/core/neighbour.c:1475) 
[    9.004888] ip_finish_output2 (kbuild/src/consumer/include/net/neighbour.h:510 kbuild/src/consumer/net/ipv4/ip_output.c:230) 
[    9.005886] ip_output (kbuild/src/consumer/net/ipv4/ip_output.c:436) 
[    9.006820] ? __ip_finish_output (kbuild/src/consumer/net/ipv4/ip_output.c:312) 


To reproduce:

        # build kernel
	cd linux
	cp config-5.11.0-rc7-02046-g4591591ab715 .config
	make HOSTCC=gcc-9 CC=gcc-9 ARCH=x86_64 olddefconfig prepare modules_prepare bzImage modules
	make HOSTCC=gcc-9 CC=gcc-9 ARCH=x86_64 INSTALL_MOD_PATH=<mod-install-dir> modules_install
	cd <mod-install-dir>
	find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz


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



Thanks,
Oliver Sang