INFO: rcu detected stall in inet_rtm_newaddr

Status: upstream: reported C repro on 2026/02/01 16:53
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+c09a9a0b8ecbc1558c8e@syzkaller.appspotmail.com
First crash: 181d, last: 181d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/02/01 linux-6.6.y (ToT) 2cf6f68313dc C [report] INFO: rcu detected stall in syscall_exit_to_user_mode
2026/02/01 upstream (ToT) 162b42445b58 C Didn't crash
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in inet_rtm_newaddr bpf net 1 4 665d 789d 0/29 auto-obsoleted due to no activity on 2025/01/03 16:01
upstream INFO: rcu detected stall in inet_rtm_newaddr (2) prio:normal net 1 syz, C error inconclusive 8 34d 452d 0/29 upstream: reported C repro on 2025/05/06 14:06
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2026/06/18 19:00 12h13m fix candidate upstream error job log
2026/04/05 09:09 1m fix candidate upstream error job log
2026/03/06 08:34 1m fix candidate upstream error job log
2026/02/02 12:54 1m fix candidate upstream error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6038/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=15845, q=689 ncpus=2)
task:syz-executor    state:R  running task     stack:21704 pid:6038  ppid:6028   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:unwind_next_frame+0x2264/0x2970 arch/x86/kernel/unwind_orc.c:682
Code: 2a e8 50 bc 4b 00 42 0f b6 04 2b 84 c0 75 46 41 c7 04 24 00 00 00 00 31 c0 48 81 c4 98 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d <c3> e8 26 bc 4b 00 e8 c1 44 c5 ff eb cf 44 89 e1 80 e1 07 80 c1 03
RSP: 0018:ffffc900037e6600 EFLAGS: 00000292
RAX: ffffffff813b5301 RBX: ffffc900037e66c0 RCX: ffff88802872da00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc900037e6690 R08: ffff88802872da00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff89137bab
R13: ffffffff8ca73388 R14: ffffffff8175b850 R15: ffffc900037e6608
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 ref_tracker_alloc+0x162/0x4c0 lib/ref_tracker.c:203
 __netdev_tracker_alloc include/linux/netdevice.h:4110 [inline]
 netdev_hold include/linux/netdevice.h:4139 [inline]
 fib_check_nh_nongw net/ipv4/fib_semantics.c:1239 [inline]
 fib_check_nh+0xd23/0x1a70 net/ipv4/fib_semantics.c:1259
 fib_create_info+0x142c/0x2460 net/ipv4/fib_semantics.c:1557
 fib_table_insert+0xc6/0x1b20 net/ipv4/fib_trie.c:1217
 fib_magic+0x2e5/0x3c0 net/ipv4/fib_frontend.c:1118
 fib_add_ifaddr+0x3fb/0x5e0 net/ipv4/fib_frontend.c:1162
 fib_inetaddr_event+0x140/0x1d0 net/ipv4/fib_frontend.c:1454
 notifier_call_chain+0x197/0x380 kernel/notifier.c:93
 blocking_notifier_call_chain+0x6a/0x90 kernel/notifier.c:388
 __inet_insert_ifa+0x9bc/0xbd0 net/ipv4/devinet.c:570
 inet_rtm_newaddr+0xc1d/0x1ae0 net/ipv4/devinet.c:986
 rtnetlink_rcv_msg+0x869/0xfa0 net/core/rtnetlink.c:6472
 netlink_rcv_skb+0x241/0x4d0 net/netlink/af_netlink.c:2545
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 __sys_sendto+0x4a9/0x6b0 net/socket.c:2200
 __do_sys_sendto net/socket.c:2212 [inline]
 __se_sys_sendto net/socket.c:2208 [inline]
 __x64_sys_sendto+0xde/0xf0 net/socket.c:2208
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9ce0f5b78e
RSP: 002b:00007ffe780c2258 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00005555776de500 RCX: 00007f9ce0f5b78e
RDX: 0000000000000028 RSI: 00007f9ce1d44670 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007ffe780c22d4 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f9ce1d44670 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10572 jiffies! g15845 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27656 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 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>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6191 Comm: syz.5.48 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:get_signal+0x4f/0x13f0 kernel/signal.c:2672
Code: 84 24 b8 00 00 00 49 be 00 00 00 00 00 fc ff df e8 76 35 32 00 65 4c 8b 3d 7e d6 ae 7e 4d 89 fc 49 8d bf 18 09 00 00 48 89 f8 <48> c1 e8 03 42 80 3c 30 00 74 05 e8 a1 5c 8a 00 4d 8b ac 24 18 09
RSP: 0018:ffffc90003457c88 EFLAGS: 00000293
RAX: ffff888028778918 RBX: 1ffff9200068afb4 RCX: ffff888028778000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888028778918
RBP: ffffc90003457ec0 R08: ffffc90003457e37 R09: 0000000000000000
R10: ffffc90003457de0 R11: fffff5200068afc7 R12: ffff888028778000
R13: dffffc0000000000 R14: dffffc0000000000 R15: ffff888028778000
FS:  000055558dc1c500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 000000002f1f6000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ffaa876d500
Code: e9 d8 00 00 00 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <c5> f9 6e c6 48 89 f8 48 83 fa 20 0f 82 cf 00 00 00 c4 e2 7d 78 c0
RSP: 002b:00007fff22be1228 EFLAGS: 00000202
RAX: 000000007fffffff RBX: 00007ffaa9545720 RCX: 0000000000000000
RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000001b2d563fb6
RBP: 0000000000000006 R08: 0000000000000000 R09: 00007ffaa8a16038
R10: 0000000000000003 R11: 0000000000000004 R12: 0000000000000044
R13: 000000000000003c R14: 0000000000000006 R15: 0000000000000004
 </TASK>
sched: RT throttling activated

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/01 16:52 linux-6.6.y 2cf6f68313dc 6b8752f2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in inet_rtm_newaddr
* Struck through repros no longer work on HEAD.