syzbot


WARNING in rt6_multipath_rebalance

Status: upstream: reported on 2025/07/25 05:47
Reported-by: syzbot+dbd8e862cb3780dae734@syzkaller.appspotmail.com
First crash: 38d, last: 22d
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in rt6_multipath_rebalance (2) net -1 292 2d15h 123d 0/29 upstream: reported on 2025/05/01 11:16
linux-6.1 WARNING in rt6_multipath_rebalance -1 3 22h09m 59d 0/3 upstream: reported on 2025/07/04 11:26
upstream WARNING in rt6_multipath_rebalance net -1 2 176d 179d 0/29 closed as invalid on 2025/04/08 14:38

Sample crash report:
veth0_macvtap: left promiscuous mode
veth1_vlan: left promiscuous mode
veth0_vlan: left promiscuous mode
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8146 at net/ipv6/route.c:4793 rt6_multipath_first_sibling net/ipv6/route.c:4715 [inline]
WARNING: CPU: 0 PID: 8146 at net/ipv6/route.c:4793 rt6_multipath_rebalance+0x44d/0x8a0 net/ipv6/route.c:4792
Modules linked in:
CPU: 0 PID: 8146 Comm: kworker/u4:2 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: netns cleanup_net
RIP: 0010:rt6_multipath_rebalance+0x44d/0x8a0 net/ipv6/route.c:4793
Code: e8 28 81 b1 f8 e9 1c fe ff ff 44 89 e1 80 e1 07 38 c1 0f 8c 85 fe ff ff 4c 89 e7 e8 cd 80 b1 f8 e9 78 fe ff ff e8 23 3b 5a f8 <0f> 0b eb 07 e8 1a 3b 5a f8 0f 0b 48 83 c4 10 5b 41 5c 41 5d 41 5e
RSP: 0018:ffffc900041ef020 EFLAGS: 00010293
RAX: ffffffff892b5a6d RBX: ffff8880312b3c00 RCX: ffff88801eec5a00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200083ddfc R12: ffff8880312b3cbe
R13: ffff8880312b3c80 R14: 0000000000000000 R15: 1ffff11006256790
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001600 CR3: 000000001a2f7000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 fib6_ifdown+0x3f3/0x4b0 net/ipv6/route.c:4913
 fib6_clean_node+0x248/0x580 net/ipv6/ip6_fib.c:2190
 fib6_walk_continue+0x672/0x900 net/ipv6/ip6_fib.c:2115
 fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2163
 fib6_clean_tree net/ipv6/ip6_fib.c:2243 [inline]
 __fib6_clean_all+0x235/0x380 net/ipv6/ip6_fib.c:2259
 rt6_sync_down_dev net/ipv6/route.c:4941 [inline]
 rt6_disable_ip+0x125/0x7a0 net/ipv6/route.c:4946
 addrconf_ifdown+0x15e/0x1880 net/ipv6/addrconf.c:3826
 addrconf_notify+0x6c6/0x1010 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x197/0x390 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2064 [inline]
 call_netdevice_notifiers net/core/dev.c:2078 [inline]
 dev_close_many+0x297/0x400 net/core/dev.c:1619
 unregister_netdevice_many_notify+0x4c1/0x1810 net/core/dev.c:11047
 unregister_netdevice_many net/core/dev.c:11130 [inline]
 default_device_exit_batch+0x9cb/0xa60 net/core/dev.c:11608
 ops_exit_list net/core/net_namespace.c:178 [inline]
 cleanup_net+0x77f/0xb90 net/core/net_namespace.c:652
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/09 21:20 linux-6.6.y 3a8ababb8b6a 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in rt6_multipath_rebalance
2025/08/05 17:25 linux-6.6.y 3a8ababb8b6a 37880f40 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in rt6_multipath_rebalance
2025/08/03 14:14 linux-6.6.y 3a8ababb8b6a 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in rt6_multipath_rebalance
2025/07/25 05:47 linux-6.6.y dbcb8d8e4163 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan WARNING in rt6_multipath_rebalance
* Struck through repros no longer work on HEAD.