Re: general protection fault in rhashtable_walk_exit

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    7c5cca358854 qmi_wwan: Support dynamic config on Quectel E..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=10ea5bb6400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
dashboard link: https://syzkaller.appspot.com/bug?extid=3f8324abccfbf8c74a9f
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1029be66400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11f7cd49400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3f8324abccfbf8c74a9f@xxxxxxxxxxxxxxxxxxxxxxxxx

RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
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: 1 PID: 6713 Comm: syz-executor470 Not tainted 4.19.0-rc2+ #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:rhashtable_walk_exit+0x74/0x360 lib/rhashtable.c:689
Code: 8e 83 c7 00 f1 f1 f1 f1 c7 40 04 00 f2 f2 f2 65 48 8b 04 25 28 00 00  
00 48 89 45 d0 31 c0 e8 13 28 f0 fd 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00  
0f 85 e5 01 00 00 48 8b 03 48 8d b8 00 01 00 00 e8
RSP: 0018:ffff8801b77d70e8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff838ea71d RDI: 0000000000000000
RBP: ffff8801b77d7188 R08: ffff8801d3334680 R09: ffffed003a877e54
R10: ffffed003a877e54 R11: ffff8801d43bf2a3 R12: 1ffff10036efae20
R13: dffffc0000000000 R14: ffff8801b77d7160 R15: dffffc0000000000
FS:  0000000002080880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004b5abc CR3: 00000001ce4b7000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tipc_dump_done+0x34/0x50 net/tipc/socket.c:3295
 __tipc_nl_compat_dumpit.isra.11+0x670/0xb30 net/tipc/netlink_compat.c:220
 tipc_nl_compat_dumpit+0x1f4/0x440 net/tipc/netlink_compat.c:267
 tipc_nl_compat_handle net/tipc/netlink_compat.c:1169 [inline]
 tipc_nl_compat_recv+0x14a0/0x19a0 net/tipc/netlink_compat.c:1207
 genl_family_rcv_msg+0x8a9/0x1140 net/netlink/genetlink.c:601
 genl_rcv_msg+0xc6/0x168 net/netlink/genetlink.c:626
 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2454
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:637
 netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
 netlink_unicast+0x5a5/0x760 net/netlink/af_netlink.c:1343
 netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1908
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:631
 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2114
 __sys_sendmsg+0x11d/0x280 net/socket.c:2152
 __do_sys_sendmsg net/socket.c:2161 [inline]
 __se_sys_sendmsg net/socket.c:2159 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2159
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441d39
Code: e8 4c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 4b 04 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffc3125798 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fffc31257b0 RCX: 0000000000441d39
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 037223c8463c1458 ]---
RIP: 0010:rhashtable_walk_exit+0x74/0x360 lib/rhashtable.c:689
Code: 8e 83 c7 00 f1 f1 f1 f1 c7 40 04 00 f2 f2 f2 65 48 8b 04 25 28 00 00  
00 48 89 45 d0 31 c0 e8 13 28 f0 fd 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00  
0f 85 e5 01 00 00 48 8b 03 48 8d b8 00 01 00 00 e8
RSP: 0018:ffff8801b77d70e8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff838ea71d RDI: 0000000000000000
RBP: ffff8801b77d7188 R08: ffff8801d3334680 R09: ffffed003a877e54
R10: ffffed003a877e54 R11: ffff8801d43bf2a3 R12: 1ffff10036efae20
R13: dffffc0000000000 R14: ffff8801b77d7160 R15: dffffc0000000000
FS:  0000000002080880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004b5abc CR3: 00000001ce4b7000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400