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: 46d, last: 19d

Sample crash report:
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: 22624 Comm: syz.3.4958 Not tainted 6.15.0-syzkaller-10402-g4cb6c8af8591 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:fib6_metric_locked include/net/ip6_fib.h:578 [inline]
RIP: 0010:rt6_mtu_change_route+0xce/0x200 net/ipv6/route.c:5061
Code: 0f 84 a6 00 00 00 4d 8d 7e 48 4c 89 f8 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 ff e8 1c 7a 08 f8 4d 8b 3f 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 04 01 00 00 41 8b 2f 89 ee 83 e6 04 31
RSP: 0018:ffffc900041ae630 EFLAGS: 00010256
RAX: 0000000000000000 RBX: ffffc900041ae9a0 RCX: 0000000000080000
RDX: ffffc9001ff47000 RSI: 0000000000001dc8 RDI: 0000000000001dc9
RBP: 0000000000000001 R08: ffff888071589e00 R09: 0000000000000003
R10: 00000000ffffffff R11: ffffffff8a1afa60 R12: dffffc0000000000
R13: ffff888026f07000 R14: ffff888026f07000 R15: 0000000000000000
FS:  00007fce6a17e6c0(0000) GS:ffff888125d65000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc6e40caff0 CR3: 000000006435d000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 fib6_clean_node+0x24d/0x590 net/ipv6/ip6_fib.c:2252
 fib6_walk_continue+0x67b/0x910 net/ipv6/ip6_fib.c:2177
 fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2225
 fib6_clean_tree net/ipv6/ip6_fib.c:2305 [inline]
 __fib6_clean_all+0x234/0x380 net/ipv6/ip6_fib.c:2321
 rt6_mtu_change+0xcb/0x110 net/ipv6/route.c:5081
 addrconf_notify+0x548/0x1010 net/ipv6/addrconf.c:3668
 notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
 call_netdevice_notifiers_mtu net/core/dev.c:2305 [inline]
 netif_set_mtu_ext+0x438/0x620 net/core/dev.c:9591
 do_setlink+0x91a/0x41c0 net/core/rtnetlink.c:3104
 rtnl_group_changelink net/core/rtnetlink.c:3773 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3927 [inline]
 rtnl_newlink+0x149f/0x1c70 net/core/rtnetlink.c:4055
 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:727
 ____sys_sendmsg+0x505/0x830 net/socket.c:2566
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
 __sys_sendmsg net/socket.c:2652 [inline]
 __do_sys_sendmsg net/socket.c:2657 [inline]
 __se_sys_sendmsg net/socket.c:2655 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fce6938e969
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:00007fce6a17e038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fce695b5fa0 RCX: 00007fce6938e969
RDX: 0000000000000000 RSI: 0000200000000280 RDI: 0000000000000005
RBP: 00007fce69410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fce695b5fa0 R15: 00007ffdbe3fb088
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fib6_metric_locked include/net/ip6_fib.h:578 [inline]
RIP: 0010:rt6_mtu_change_route+0xce/0x200 net/ipv6/route.c:5061
Code: 0f 84 a6 00 00 00 4d 8d 7e 48 4c 89 f8 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 ff e8 1c 7a 08 f8 4d 8b 3f 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 04 01 00 00 41 8b 2f 89 ee 83 e6 04 31
RSP: 0018:ffffc900041ae630 EFLAGS: 00010256
RAX: 0000000000000000 RBX: ffffc900041ae9a0 RCX: 0000000000080000
RDX: ffffc9001ff47000 RSI: 0000000000001dc8 RDI: 0000000000001dc9
RBP: 0000000000000001 R08: ffff888071589e00 R09: 0000000000000003
R10: 00000000ffffffff R11: ffffffff8a1afa60 R12: dffffc0000000000
R13: ffff888026f07000 R14: ffff888026f07000 R15: 0000000000000000
FS:  00007fce6a17e6c0(0000) GS:ffff888125d65000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc6e40caff0 CR3: 000000006435d000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
   0:	0f 84 a6 00 00 00    	je     0xac
   6:	4d 8d 7e 48          	lea    0x48(%r14),%r15
   a:	4c 89 f8             	mov    %r15,%rax
   d:	48 c1 e8 03          	shr    $0x3,%rax
  11:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1)
  16:	74 08                	je     0x20
  18:	4c 89 ff             	mov    %r15,%rdi
  1b:	e8 1c 7a 08 f8       	call   0xf8087a3c
  20:	4d 8b 3f             	mov    (%r15),%r15
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 04 01 00 00    	jne    0x13b
  37:	41 8b 2f             	mov    (%r15),%ebp
  3a:	89 ee                	mov    %ebp,%esi
  3c:	83 e6 04             	and    $0x4,%esi
  3f:	31                   	.byte 0x31

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/01 11:09 upstream 4cb6c8af8591 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root general protection fault in rt6_mtu_change_route
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
2025/05/12 02:33 upstream cd802e7e5f1e 77908e5f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream general protection fault in rt6_mtu_change_route
* Struck through repros no longer work on HEAD.