syzbot


general protection fault in rt6_insert_exception

Status: upstream: reported on 2026/05/04 06:39
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+01f005f9c6387ca6f6dd@syzkaller.appspotmail.com
First crash: 2d09h, last: 2d09h
Discussions (2)
Title Replies (including bot) Last reply
[PATCH v1 net] ipv6: Fix null-ptr-deref in fib6_mtu(). 3 (3) 2026/05/06 00:40
[syzbot] [net?] general protection fault in rt6_insert_exception 0 (1) 2026/05/04 06:39

Sample crash report:
kvm_intel: set kvm_intel.dump_invalid_vmcs=1 to dump internal KVM state.
Oops: general protection fault, probably for non-canonical address 0xdffffc00000000bc: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x00000000000005e0-0x00000000000005e7]
CPU: 0 UID: 0 PID: 7890 Comm: syz.2.502 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:fib6_mtu net/ipv6/route.c:1648 [inline]
RIP: 0010:rt6_insert_exception+0x9eb/0x10a0 net/ipv6/route.c:1753
Code: 3b 14 cf f7 45 85 f6 0f 85 1d 02 00 00 e8 7d 19 cf f7 48 8d bb e0 05 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 89
RSP: 0000:ffffc9000610f120 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000c001000
RDX: 00000000000000bc RSI: ffffffff8a38bc83 RDI: 00000000000005e0
RBP: ffff888052f06000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888042d16c00
R13: ffff888042d16cc8 R14: 0000000000000001 R15: 0000000000000500
FS:  0000000000000000(0000) GS:ffff88809717d000(0063) knlGS:00000000f540db40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f73c6d50 CR3: 000000006eff0000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __ip6_rt_update_pmtu+0x555/0xd60 net/ipv6/route.c:2982
 ip6_update_pmtu+0x34f/0x3b0 net/ipv6/route.c:3014
 icmpv6_err+0x2a2/0x3f0 net/ipv6/icmp.c:82
 icmpv6_notify+0x35e/0x820 net/ipv6/icmp.c:1087
 icmpv6_rcv+0x10bf/0x1ae0 net/ipv6/icmp.c:1228
 ip6_protocol_deliver_rcu+0xf97/0x1500 net/ipv6/ip6_input.c:478
 ip6_input_finish+0x1e4/0x4a0 net/ipv6/ip6_input.c:529
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ip6_input+0x105/0x2f0 net/ipv6/ip6_input.c:540
 ip6_mc_input+0x513/0xf50 net/ipv6/ip6_input.c:630
 dst_input include/net/dst.h:480 [inline]
 ip6_rcv_finish net/ipv6/ip6_input.c:119 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ipv6_rcv+0x34c/0x3d0 net/ipv6/ip6_input.c:351
 __netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:6202
 __netif_receive_skb+0x1f/0x120 net/core/dev.c:6315
 netif_receive_skb_internal net/core/dev.c:6401 [inline]
 netif_receive_skb+0x13b/0x7f0 net/core/dev.c:6460
 tun_rx_batched.isra.0+0x3f6/0x750 drivers/net/tun.c:1511
 tun_get_user+0x1e31/0x3c20 drivers/net/tun.c:1955
 tun_chr_write_iter+0xdc/0x200 drivers/net/tun.c:2001
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 do_int80_emulation+0x141/0x700 arch/x86/entry/syscall_32.c:172
 asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:621
RIP: 0023:0xf715616b
Code: 57 56 53 8b 44 24 14 f6 00 08 75 23 8b 44 24 18 8b 5c 24 1c 8b 4c 24 20 8b 54 24 24 8b 74 24 28 8b 7c 24 2c 8b 6c 24 30 cd 80 <5b> 5e 5f 5d c3 5b 5e 5f 5d e9 f7 a1 ff ff 66 90 66 90 66 90 90 53
RSP: 002b:00000000f540d44c EFLAGS: 00000246 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 00000000000000c8 RCX: 0000000080000640
RDX: 000000000000007a RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fib6_mtu net/ipv6/route.c:1648 [inline]
RIP: 0010:rt6_insert_exception+0x9eb/0x10a0 net/ipv6/route.c:1753
Code: 3b 14 cf f7 45 85 f6 0f 85 1d 02 00 00 e8 7d 19 cf f7 48 8d bb e0 05 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 89
RSP: 0000:ffffc9000610f120 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000c001000
RDX: 00000000000000bc RSI: ffffffff8a38bc83 RDI: 00000000000005e0
RBP: ffff888052f06000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888042d16c00
R13: ffff888042d16cc8 R14: 0000000000000001 R15: 0000000000000500
FS:  0000000000000000(0000) GS:ffff88809717d000(0063) knlGS:00000000f540db40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f73c6d50 CR3: 000000006eff0000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	3b 14 cf             	cmp    (%rdi,%rcx,8),%edx
   3:	f7 45 85 f6 0f 85 1d 	testl  $0x1d850ff6,-0x7b(%rbp)
   a:	02 00                	add    (%rax),%al
   c:	00 e8                	add    %ch,%al
   e:	7d 19                	jge    0x29
  10:	cf                   	iret
  11:	f7 48 8d bb e0 05 00 	testl  $0x5e0bb,-0x73(%rax)
  18:	00 48 b8             	add    %cl,-0x48(%rax)
  1b:	00 00                	add    %al,(%rax)
  1d:	00 00                	add    %al,(%rax)
  1f:	00 fc                	add    %bh,%ah
  21:	ff                   	lcall  (bad)
  22:	df 48 89             	fisttps -0x77(%rax)
  25:	fa                   	cli
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2e:	48 89 f8             	mov    %rdi,%rax
  31:	83 e0 07             	and    $0x7,%eax
  34:	83 c0 03             	add    $0x3,%eax
  37:	38 d0                	cmp    %dl,%al
  39:	7c 08                	jl     0x43
  3b:	84 d2                	test   %dl,%dl
  3d:	0f                   	.byte 0xf
  3e:	85                   	.byte 0x85
  3f:	89                   	.byte 0x89

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/03 16:35 upstream 66edb901bf87 a0d91488 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 general protection fault in rt6_insert_exception
* Struck through repros no longer work on HEAD.