BUG: spinlock bad magic in rhashtable_walk_enter

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    510e2ced ipv6: fix src addr routing with the exception table
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=11e25b02a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=82f0809e8f0a8c87
dashboard link: https://syzkaller.appspot.com/bug?extid=01dd5c4b3c34a5cf9308
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16b6373ca00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1251e73ca00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+01dd5c4b3c34a5cf9308@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: spinlock bad magic on CPU#0, syz-executor715/8517
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8517 Comm: syz-executor715 Not tainted 5.1.0+ #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:task_pid_nr include/linux/sched.h:1241 [inline]
RIP: 0010:spin_dump.cold+0xa2/0xe6 kernel/locking/spinlock_debug.c:65
Code: ae 4c 02 00 e8 75 5d bf 05 58 5b 41 5c 41 5d 41 5e 5d c3 48 8d bb d0  
04 00 00 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 <0f> b6 04 02 84  
c0 74 04 3c 03 7e 24 44 8b ab d0 04 00 00 48 81 c3
RSP: 0018:ffff888086267538 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000078e05280 RCX: 0000000000000000
RDX: 000000000f1c0aea RSI: ffffffff815afbe6 RDI: 0000000078e05750
RBP: ffff888086267560 R08: 0000000000000036 R09: ffffed1015d06011
R10: ffffed1015d06010 R11: ffff8880ae830087 R12: ffff888216427ba8
R13: ffff88808e534300 R14: ffff888216426980 R15: ffff8880862675d8
FS:  0000000000b40880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000204 CR3: 0000000098123000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 spin_bug kernel/locking/spinlock_debug.c:75 [inline]
 debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline]
 do_raw_spin_lock+0x231/0x2e0 kernel/locking/spinlock_debug.c:112
 __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_lock+0x37/0x40 kernel/locking/spinlock.c:151
 spin_lock include/linux/spinlock.h:338 [inline]
 rhashtable_walk_enter+0xf9/0x390 lib/rhashtable.c:669
 __tipc_dump_start+0x1fa/0x3c0 net/tipc/socket.c:3414
 tipc_dump_start+0x70/0x90 net/tipc/socket.c:3396
 __netlink_dump_start+0x4fb/0x7e0 net/netlink/af_netlink.c:2351
 netlink_dump_start include/linux/netlink.h:226 [inline]
 tipc_sock_diag_handler_dump+0x1d9/0x270 net/tipc/diag.c:91
 __sock_diag_cmd net/core/sock_diag.c:232 [inline]
 sock_diag_rcv_msg+0x322/0x410 net/core/sock_diag.c:263
 netlink_rcv_skb+0x17a/0x460 net/netlink/af_netlink.c:2486
 sock_diag_rcv+0x2b/0x40 net/core/sock_diag.c:274
 netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
 netlink_unicast+0x536/0x720 net/netlink/af_netlink.c:1337
 netlink_sendmsg+0x8ae/0xd70 net/netlink/af_netlink.c:1926
 sock_sendmsg_nosec net/socket.c:660 [inline]
 sock_sendmsg+0x12e/0x170 net/socket.c:671
 ___sys_sendmsg+0x81d/0x960 net/socket.c:2292
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2330
 __do_sys_sendmsg net/socket.c:2339 [inline]
 __se_sys_sendmsg net/socket.c:2337 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2337
 do_syscall_64+0x103/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4401f9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffce875faa8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401f9
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a80
R13: 0000000000401b10 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 3bee47f081c674b7 ]---
RIP: 0010:task_pid_nr include/linux/sched.h:1241 [inline]
RIP: 0010:spin_dump.cold+0xa2/0xe6 kernel/locking/spinlock_debug.c:65
Code: ae 4c 02 00 e8 75 5d bf 05 58 5b 41 5c 41 5d 41 5e 5d c3 48 8d bb d0  
04 00 00 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 <0f> b6 04 02 84  
c0 74 04 3c 03 7e 24 44 8b ab d0 04 00 00 48 81 c3
RSP: 0018:ffff888086267538 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000078e05280 RCX: 0000000000000000
RDX: 000000000f1c0aea RSI: ffffffff815afbe6 RDI: 0000000078e05750
RBP: ffff888086267560 R08: 0000000000000036 R09: ffffed1015d06011
R10: ffffed1015d06010 R11: ffff8880ae830087 R12: ffff888216427ba8
R13: ffff88808e534300 R14: ffff888216426980 R15: ffff8880862675d8
FS:  0000000000b40880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000204 CR3: 0000000098123000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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