INFO: rcu detected stall in fib_nl_delrule (2)

Status: upstream: reported on 2026/07/04 02:41
Reported-by: syzbot+c944e095db7e9be300e4@syzkaller.appspotmail.com
First crash: 24d, last: 22d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in fib_nl_delrule 1 1 223d 223d 0/3 auto-obsoleted due to no activity on 2026/03/27 18:20
linux-5.15 INFO: rcu detected stall in fib_nl_delrule 1 1 321d 321d 0/3 auto-obsoleted due to no activity on 2025/12/19 19:08

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (3 ticks this GP) idle=b91/1/0x4000000000000002 softirq=7150/7150 fqs=0 
	(detected by 1, t=10502 jiffies, g=8429, q=1569)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4529 Comm: syz.2.67 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:kasan_check_range+0x1b7/0x290 mm/kasan/generic.c:189
Code: 49 8d 5f 07 4d 85 ff 49 0f 49 df 48 83 e3 f8 49 29 df 74 0e 41 80 3b 00 75 69 49 ff c3 49 ff cf 75 f2 5b 41 5c 41 5e 41 5f 5d <c3> 45 84 ff 0f 85 91 00 00 00 41 f7 c7 00 ff 00 00 0f 85 89 00 00
RSP: 0018:ffffc90000006ff8 EFLAGS: 00000056
RAX: 0000000000000001 RBX: 0000000000000010 RCX: ffffffff81654fb6
RDX: 0000000000000001 RSI: 0000000000000010 RDI: ffff8880b903b1f0
RBP: 0000000000000000 R08: ffff8880b903b1ff R09: 1ffff1101720763f
R10: dffffc0000000000 R11: ffffed1017207640 R12: ffff8880b903b208
R13: dffffc0000000000 R14: ffff8880b903b1f0 R15: 1ffff11017207641
FS:  00007fd590ad56c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 000000005fa25000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 memset+0x1e/0x40 mm/kasan/shadow.c:44
 init_irq_work include/linux/irq_work.h:36 [inline]
 rcu_read_unlock_special+0x326/0x4a0 kernel/rcu/tree_plugin.h:665
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 __perf_event_output kernel/events/core.c:7813 [inline]
 perf_event_output_forward+0x255/0x2e0 kernel/events/core.c:7822
 __perf_event_overflow+0x35f/0x550 kernel/events/core.c:9515
 perf_tp_event+0x324/0xbe0 kernel/events/core.c:10047
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
 perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 c2 22 9d 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007780 EFLAGS: 00000206
RAX: 0c8e66cb1c80bf00 RBX: 1ffff92000000ef4 RCX: 0c8e66cb1c80bf00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a2a40
RBP: ffffc90000007860 R08: ffffffff901e91bf R09: 1ffffffff203d237
R10: dffffc0000000000 R11: fffffbfff203d238 R12: ffffffff8c323400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 ndisc_send_skb+0xd39/0x1410 net/ipv6/ndisc.c:521
 addrconf_rs_timer+0x367/0x640 net/ipv6/addrconf.c:3959
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:168 [inline]
RIP: 0010:unwind_next_frame+0x1ae/0x1cf0 arch/x86/kernel/unwind_orc.c:448
Code: 00 00 89 e8 4c 8d 24 85 2c a0 9e 8e 4c 89 e0 48 c1 e8 03 49 bf 00 00 00 00 00 fc ff df 42 0f b6 04 38 84 c0 0f 85 dd 15 00 00 <45> 8b 24 24 89 e8 ff c0 4c 8d 2c 85 2c a0 9e 8e 4c 89 e8 48 c1 e8
RSP: 0018:ffffc9000329eaf0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc9000329eb88 RCX: ffffffff962eff00
RDX: dffffc0000000000 RSI: 0000000000090081 RDI: ffffffff81350ed7
RBP: 000000000008bedf R08: ffffc9000329ec50 R09: 000000000000000f
R10: dffffc0000000000 R11: fffff52000653d7d R12: ffffffff8ec19ba8
R13: ffffc9000329ff20 R14: ffffffff89bedf2b R15: dffffc0000000000
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 __kasan_slab_alloc+0x92/0xc0 mm/kasan/common.c:467
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x15d/0x280 mm/slub.c:3238
 leaf_new net/ipv4/fib_trie.c:357 [inline]
 fib_insert_node net/ipv4/fib_trie.c:1109 [inline]
 fib_insert_alias+0x300/0x1280 net/ipv4/fib_trie.c:1159
 fib_trie_unmerge+0x308/0xce0 net/ipv4/fib_trie.c:1906
 fib_unmerge+0xbc/0x350 net/ipv4/fib_frontend.c:160
 fib4_rule_delete+0x41/0x3e0 net/ipv4/fib_rules.c:293
 fib_nl_delrule+0x1657/0x1ee0 net/core/fib_rules.c:907
 rtnetlink_rcv_msg+0x82c/0xf00 net/core/rtnetlink.c:5688
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2512
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1923
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
 __sys_sendmsg net/socket.c:2529 [inline]
 __do_sys_sendmsg net/socket.c:2538 [inline]
 __se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd59289de59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd590ad5028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd592b26090 RCX: 00007fd59289de59
RDX: 0000000000000000 RSI: 0000200000000940 RDI: 0000000000000007
RBP: 00007fd592933e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd592b26128 R14: 00007fd592b26090 R15: 00007ffd9a0b1428
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g8429 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=2551
rcu: rcu_preempt kthread starved for 10502 jiffies! g8429 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27872 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9a/0x370 kernel/rcu/tree.c:2145
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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: 4529 Comm: syz.2.67 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4702 [inline]
RIP: 0010:__lock_acquire+0x713/0x7b50 kernel/locking/lockdep.c:4962
Code: 10 0b 00 00 48 89 d8 48 c1 e8 03 42 0f b6 04 00 84 c0 75 44 8b 1b 48 8b 44 24 30 42 0f b6 04 00 84 c0 75 54 48 8b 04 24 33 18 <41> ff ce 49 ff cf f7 c3 00 60 00 00 74 a6 e9 20 01 00 00 48 c7 c7
RSP: 0018:ffffc90000006da0 EFLAGS: 00000002
RAX: ffff88802c344708 RBX: 00000000000e07ea RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff901e90c0
RBP: ffffc90000006fd0 R08: dffffc0000000000 R09: 1ffffffff203d218
R10: dffffc0000000000 R11: fffffbfff203d219 R12: 0000000000000000
R13: ffff88802c343b80 R14: 0000000000000003 R15: 0000000000000001
FS:  00007fd590ad56c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000010000 CR3: 000000005fa25000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 __perf_event_output kernel/events/core.c:7800 [inline]
 perf_event_output_forward+0xbc/0x2e0 kernel/events/core.c:7822
 __perf_event_overflow+0x35f/0x550 kernel/events/core.c:9515
 perf_tp_event+0x324/0xbe0 kernel/events/core.c:10047
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
 perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 c2 22 9d 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007780 EFLAGS: 00000206
RAX: 0c8e66cb1c80bf00 RBX: 1ffff92000000ef4 RCX: 0c8e66cb1c80bf00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a2a40
RBP: ffffc90000007860 R08: ffffffff901e91bf R09: 1ffffffff203d237
R10: dffffc0000000000 R11: fffffbfff203d238 R12: ffffffff8c323400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 ndisc_send_skb+0xd39/0x1410 net/ipv6/ndisc.c:521
 addrconf_rs_timer+0x367/0x640 net/ipv6/addrconf.c:3959
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:168 [inline]
RIP: 0010:unwind_next_frame+0x1ae/0x1cf0 arch/x86/kernel/unwind_orc.c:448
Code: 00 00 89 e8 4c 8d 24 85 2c a0 9e 8e 4c 89 e0 48 c1 e8 03 49 bf 00 00 00 00 00 fc ff df 42 0f b6 04 38 84 c0 0f 85 dd 15 00 00 <45> 8b 24 24 89 e8 ff c0 4c 8d 2c 85 2c a0 9e 8e 4c 89 e8 48 c1 e8
RSP: 0018:ffffc9000329eaf0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc9000329eb88 RCX: ffffffff962eff00
RDX: dffffc0000000000 RSI: 0000000000090081 RDI: ffffffff81350ed7
RBP: 000000000008bedf R08: ffffc9000329ec50 R09: 000000000000000f
R10: dffffc0000000000 R11: fffff52000653d7d R12: ffffffff8ec19ba8
R13: ffffc9000329ff20 R14: ffffffff89bedf2b R15: dffffc0000000000
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 __kasan_slab_alloc+0x92/0xc0 mm/kasan/common.c:467
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x15d/0x280 mm/slub.c:3238
 leaf_new net/ipv4/fib_trie.c:357 [inline]
 fib_insert_node net/ipv4/fib_trie.c:1109 [inline]
 fib_insert_alias+0x300/0x1280 net/ipv4/fib_trie.c:1159
 fib_trie_unmerge+0x308/0xce0 net/ipv4/fib_trie.c:1906
 fib_unmerge+0xbc/0x350 net/ipv4/fib_frontend.c:160
 fib4_rule_delete+0x41/0x3e0 net/ipv4/fib_rules.c:293
 fib_nl_delrule+0x1657/0x1ee0 net/core/fib_rules.c:907
 rtnetlink_rcv_msg+0x82c/0xf00 net/core/rtnetlink.c:5688
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2512
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1923
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
 __sys_sendmsg net/socket.c:2529 [inline]
 __do_sys_sendmsg net/socket.c:2538 [inline]
 __se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd59289de59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd590ad5028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd592b26090 RCX: 00007fd59289de59
RDX: 0000000000000000 RSI: 0000200000000940 RDI: 0000000000000007
RBP: 00007fd592933e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd592b26128 R14: 00007fd592b26090 R15: 00007ffd9a0b1428
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/06 05:36 linux-5.15.y c86c4726e7f0 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in fib_nl_delrule
2026/07/04 02:40 linux-5.15.y eceeec79dbc6 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in fib_nl_delrule
* Struck through repros no longer work on HEAD.