syzbot


general protection fault in fib_lookup_good_nhc

Status: upstream: reported on 2025/07/01 19:21
Reported-by: syzbot+1bec090fcfa0ab7bcbb8@syzkaller.appspotmail.com
First crash: 19d, last: 5d23h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in fib_lookup_good_nhc net 2 1 76d 76d 0/29 closed as invalid on 2025/06/04 11:51
upstream Internal error in fib_lookup_good_nhc net 2 1 792d 791d 0/29 auto-obsoleted due to no activity on 2023/08/18 23:40

Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc000000006b: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000358-0x000000000000035f]
CPU: 1 PID: 10736 Comm: syz.5.1595 Not tainted 5.15.188-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:ip_ignore_linkdown include/linux/inetdevice.h:254 [inline]
RIP: 0010:fib_lookup_good_nhc+0x81/0x3d0 net/ipv4/fib_trie.c:1407
Code: 4c 89 24 24 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 1f b8 51 f9 41 bc 58 03 00 00 4c 03 23 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 00 b8 51 f9 4d 8b 24 24 e8 07 0f
RSP: 0018:ffffc900032be478 EFLAGS: 00010202
RAX: 000000000000006b RBX: ffff88802a091620 RCX: ffff88802b630000
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88802a09162f R08: dffffc0000000000 R09: fffffbfff1ff7619
R10: fffffbfff1ff7619 R11: 1ffffffff1ff7618 R12: 0000000000000358
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff110054122c5
FS:  00007fa389d0d6c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f932d7e4286 CR3: 000000005db2e000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 nexthop_get_nhc_lookup+0x1a8/0x400 include/net/nexthop.h:405
 fib_table_lookup+0xe76/0x15e0 net/ipv4/fib_trie.c:1583
 fib4_rule_action+0x1cf/0x2f0 net/ipv4/fib_rules.c:135
 fib_rules_lookup+0x5ab/0xaf0 net/core/fib_rules.c:318
 __fib_lookup+0xf6/0x200 net/ipv4/fib_rules.c:92
 ip_route_output_key_hash_rcu+0x305/0x2460 net/ipv4/route.c:2785
 ip_route_output_key_hash+0x1b1/0x2e0 net/ipv4/route.c:2675
 __ip_route_output_key include/net/route.h:126 [inline]
 ip_route_output_flow+0x26/0x150 net/ipv4/route.c:2905
 ip_route_output_ports include/net/route.h:169 [inline]
 ipip6_tunnel_bind_dev+0x211/0x630 net/ipv6/sit.c:1114
 ipip6_tunnel_init+0x9e/0x2f0 net/ipv6/sit.c:1457
 register_netdevice+0x612/0x16b0 net/core/dev.c:10327
 ipip6_tunnel_create+0x18b/0x400 net/ipv6/sit.c:215
 ipip6_newlink+0x2de/0x770 net/ipv6/sit.c:1643
 __rtnl_newlink net/core/rtnetlink.c:3524 [inline]
 rtnl_newlink+0x114c/0x17d0 net/core/rtnetlink.c:3572
 rtnetlink_rcv_msg+0x9b9/0xe60 net/core/rtnetlink.c:5650
 netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2489
 netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
 netlink_unicast+0x77c/0x920 net/netlink/af_netlink.c:1337
 netlink_sendmsg+0x8ab/0xbc0 net/netlink/af_netlink.c:1905
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2436
 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2490
 __sys_sendmsg net/socket.c:2519 [inline]
 __do_sys_sendmsg net/socket.c:2528 [inline]
 __se_sys_sendmsg+0x190/0x250 net/socket.c:2526
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa38bea5929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa389d0d038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fa38c0ccfa0 RCX: 00007fa38bea5929
RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000005
RBP: 00007fa38bf27b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa38c0ccfa0 R15: 00007ffc83a94ec8
 </TASK>
Modules linked in:
---[ end trace 10d7dacc81d206b2 ]---
RIP: 0010:ip_ignore_linkdown include/linux/inetdevice.h:254 [inline]
RIP: 0010:fib_lookup_good_nhc+0x81/0x3d0 net/ipv4/fib_trie.c:1407
Code: 4c 89 24 24 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 1f b8 51 f9 41 bc 58 03 00 00 4c 03 23 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 00 b8 51 f9 4d 8b 24 24 e8 07 0f
RSP: 0018:ffffc900032be478 EFLAGS: 00010202
RAX: 000000000000006b RBX: ffff88802a091620 RCX: ffff88802b630000
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88802a09162f R08: dffffc0000000000 R09: fffffbfff1ff7619
R10: fffffbfff1ff7619 R11: 1ffffffff1ff7618 R12: 0000000000000358
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff110054122c5
FS:  00007fa389d0d6c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa389cebf98 CR3: 000000005db2e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	4c 89 24 24          	mov    %r12,(%rsp)
   4:	48 89 d8             	mov    %rbx,%rax
   7:	48 c1 e8 03          	shr    $0x3,%rax
   b:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)
  10:	74 08                	je     0x1a
  12:	48 89 df             	mov    %rbx,%rdi
  15:	e8 1f b8 51 f9       	call   0xf951b839
  1a:	41 bc 58 03 00 00    	mov    $0x358,%r12d
  20:	4c 03 23             	add    (%rbx),%r12
  23:	4c 89 e0             	mov    %r12,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	4c 89 e7             	mov    %r12,%rdi
  34:	e8 00 b8 51 f9       	call   0xf951b839
  39:	4d 8b 24 24          	mov    (%r12),%r12
  3d:	e8                   	.byte 0xe8
  3e:	07                   	(bad)
  3f:	0f                   	.byte 0xf

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/15 08:04 linux-5.15.y 89950c454265 03fcfc4b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in fib_lookup_good_nhc
2025/07/10 20:44 linux-5.15.y 2f693b607545 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in fib_lookup_good_nhc
2025/07/10 06:46 linux-5.15.y 3dea0e7f549e 956bd956 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in fib_lookup_good_nhc
2025/07/04 03:32 linux-5.15.y 3dea0e7f549e 76ad128c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in fib_lookup_good_nhc
2025/07/01 19:21 linux-5.15.y 3dea0e7f549e 091a06cd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in fib_lookup_good_nhc
* Struck through repros no longer work on HEAD.