general protection fault in find_match

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c3038e71 Linux 4.19.80
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=134545f8e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=44c623b7e5432cee
dashboard link: https://syzkaller.appspot.com/bug?extid=3e1695528a9f85ad3b77
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e74070e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15837f37600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3e1695...@syzkaller.appspotmail.com

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: 8273 Comm: syz-executor030 Not tainted 4.19.80 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:fib6_ignore_linkdown net/ipv6/route.c:651 [inline]
RIP: 0010:find_match+0x153/0xe20 net/ipv6/route.c:667
Code: 0f b6 75 a8 40 84 f6 0f 84 76 06 00 00 e8 55 be 6e fb 49 8d bf 3c 02
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 dd
RSP: 0018:ffff888089356fb8 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: 0000000000000003 RCX: ffffffff85fc0f72
RDX: 0000000000000047 RSI: ffffffff85fc08eb RDI: 000000000000023c
RBP: ffff888089357020 R08: ffff8880a1e48580 R09: ffffed1015d04733
R10: ffffed1015d04732 R11: ffff8880ae823993 R12: 0000000000000000
R13: ffff8880a4b73200 R14: ffff8880a4b73140 R15: 0000000000000000
FS: 00007f4da32fe700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 0000000099fd3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
find_rr_leaf net/ipv6/route.c:713 [inline]
rt6_select net/ipv6/route.c:763 [inline]
fib6_table_lookup+0x48e/0xce0 net/ipv6/route.c:1870
ip6_pol_route+0x1a4/0xfa0 net/ipv6/route.c:1903
ip6_pol_route_output+0x54/0x70 net/ipv6/route.c:2129
fib6_rule_lookup+0x125/0x550 net/ipv6/fib6_rules.c:118
ip6_route_output_flags+0x2c4/0x350 net/ipv6/route.c:2157
ip6_dst_lookup_tail+0x571/0x1a70 net/ipv6/ip6_output.c:979
ip6_dst_lookup_flow+0xa8/0x220 net/ipv6/ip6_output.c:1080
ip6_sk_dst_lookup_flow net/ipv6/ip6_output.c:1118 [inline]
ip6_sk_dst_lookup_flow+0x5c3/0xad0 net/ipv6/ip6_output.c:1108
udpv6_sendmsg+0x17ad/0x28d0 net/ipv6/udp.c:1383
inet_sendmsg+0x141/0x5d0 net/ipv4/af_inet.c:798
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:632
___sys_sendmsg+0x3e2/0x920 net/socket.c:2115
__sys_sendmmsg+0x1bf/0x4e0 net/socket.c:2210
__do_sys_sendmmsg net/socket.c:2239 [inline]
__se_sys_sendmmsg net/socket.c:2236 [inline]
__x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2236
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447979
Code: e8 8c e7 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 fb 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4da32fdd98 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00000000006dcc28 RCX: 0000000000447979
RDX: 00000000000000c6 RSI: 0000000020006d00 RDI: 0000000000000004
RBP: 00000000006dcc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc2c
R13: 300300306d616574 R14: 0000000000000000 R15: 010000306d616574
Modules linked in:
---[ end trace 037660a5726b98ed ]---
RIP: 0010:fib6_ignore_linkdown net/ipv6/route.c:651 [inline]
RIP: 0010:find_match+0x153/0xe20 net/ipv6/route.c:667
Code: 0f b6 75 a8 40 84 f6 0f 84 76 06 00 00 e8 55 be 6e fb 49 8d bf 3c 02
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 dd
RSP: 0018:ffff888089356fb8 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: 0000000000000003 RCX: ffffffff85fc0f72
RDX: 0000000000000047 RSI: ffffffff85fc08eb RDI: 000000000000023c
RBP: ffff888089357020 R08: ffff8880a1e48580 R09: ffffed1015d04733
R10: ffffed1015d04732 R11: ffff8880ae823993 R12: 0000000000000000
R13: ffff8880a4b73200 R14: ffff8880a4b73140 R15: 0000000000000000
FS: 00007f4da32fe700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 0000000099fd3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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