syzbot


general protection fault in rt6_mtu_change_route

Status: moderation: reported on 2025/05/05 06:43
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+907a437a5754e3c2e7de@syzkaller.appspotmail.com
First crash: 20h17m, last: 20h17m

Sample crash report:
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=17380 comm=syz.8.3029
netlink: 'syz.8.3029': attribute type 1 has an invalid length.
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 17380 Comm: syz.8.3029 Not tainted 6.15.0-rc4-syzkaller-00296-ge8ab83e34bdc #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
RIP: 0010:fib6_metric_locked include/net/ip6_fib.h:577 [inline]
RIP: 0010:rt6_mtu_change_route+0xbc/0x290 net/ipv6/route.c:5008
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 c7 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 48 48 89 ea 48 c1 ea 03 <0f> b6 14 02 48 89 e8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 75
RSP: 0018:ffffc9000435eb18 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff88814e13d000 RCX: ffffc9000ec79000
RDX: 0000000000000000 RSI: ffffffff8a1bf508 RDI: ffff88814e13d048
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffc9000435ee50
R13: ffff8880334f1000 R14: fffff5200086bda9 R15: fffff5200086bda7
FS:  00007f205e1f66c0(0000) GS:ffff888124adf000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c45ab1b CR3: 000000005d077000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 fib6_clean_node+0x2a4/0x5b0 net/ipv6/ip6_fib.c:2199
 fib6_walk_continue+0x44f/0x8d0 net/ipv6/ip6_fib.c:2124
 fib6_walk+0x182/0x370 net/ipv6/ip6_fib.c:2172
 fib6_clean_tree+0xd4/0x110 net/ipv6/ip6_fib.c:2252
 __fib6_clean_all+0x107/0x2d0 net/ipv6/ip6_fib.c:2268
 rt6_mtu_change+0xb8/0x100 net/ipv6/route.c:5028
 addrconf_notify+0x5f2/0x19e0 net/ipv6/addrconf.c:3665
 notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2176
 call_netdevice_notifiers_mtu net/core/dev.c:2251 [inline]
 netif_set_mtu_ext+0x3bf/0x5c0 net/core/dev.c:9499
 netif_set_mtu+0xb0/0x160 net/core/dev.c:9520
 dev_set_mtu+0xb2/0x260 net/core/dev_api.c:247
 ip_tunnel_newlink+0x42d/0x8f0 net/ipv4/ip_tunnel.c:1257
 ipgre_newlink+0x1c5/0x240 net/ipv4/ip_gre.c:1416
 rtnl_newlink_create net/core/rtnetlink.c:3833 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3950 [inline]
 rtnl_newlink+0xc42/0x2000 net/core/rtnetlink.c:4065
 rtnetlink_rcv_msg+0x95b/0xe90 net/core/rtnetlink.c:6955
 netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg net/socket.c:727 [inline]
 ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620
 __sys_sendmsg+0x16d/0x220 net/socket.c:2652
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f206038e969
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:00007f205e1f6038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f20605b5fa0 RCX: 00007f206038e969
RDX: 0000000000040004 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f2060410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f20605b5fa0 R15: 00007ffc71438e18
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fib6_metric_locked include/net/ip6_fib.h:577 [inline]
RIP: 0010:rt6_mtu_change_route+0xbc/0x290 net/ipv6/route.c:5008
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 c7 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 48 48 89 ea 48 c1 ea 03 <0f> b6 14 02 48 89 e8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 75
RSP: 0018:ffffc9000435eb18 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff88814e13d000 RCX: ffffc9000ec79000
RDX: 0000000000000000 RSI: ffffffff8a1bf508 RDI: ffff88814e13d048
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffc9000435ee50
R13: ffff8880334f1000 R14: fffff5200086bda9 R15: fffff5200086bda7
FS:  00007f205e1f66c0(0000) GS:ffff888124adf000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c45ab1b CR3: 000000005d077000 CR4: 00000000003526f0
----------------
Code disassembly (best guess), 3 bytes skipped:
   0:	df 48 89             	fisttps -0x77(%rax)
   3:	fa                   	cli
   4:	48 c1 ea 03          	shr    $0x3,%rdx
   8:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   c:	0f 85 c7 01 00 00    	jne    0x1d9
  12:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  19:	fc ff df
  1c:	48 8b 6b 48          	mov    0x48(%rbx),%rbp
  20:	48 89 ea             	mov    %rbp,%rdx
  23:	48 c1 ea 03          	shr    $0x3,%rdx
* 27:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2b:	48 89 e8             	mov    %rbp,%rax
  2e:	83 e0 07             	and    $0x7,%eax
  31:	83 c0 03             	add    $0x3,%eax
  34:	38 d0                	cmp    %dl,%al
  36:	7c 08                	jl     0x40
  38:	84 d2                	test   %dl,%dl
  3a:	0f                   	.byte 0xf
  3b:	85                   	.byte 0x85
  3c:	75                   	.byte 0x75

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/05 01:49 upstream e8ab83e34bdc b0714e37 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root general protection fault in rt6_mtu_change_route
* Struck through repros no longer work on HEAD.