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: 111d, last: 18d
▶ ▼ 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 309d 309d 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 407d 407d 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-....: (49 ticks this GP) idle=369/1/0x4000000000000002 softirq=11851/11851 fqs=2111 
	(detected by 1, t=10506 jiffies, g=15933, q=1659)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6252 Comm: syz.2.468 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:unwind_get_return_address+0x25/0x80 arch/x86/kernel/unwind_orc.c:320
Code: 00 00 00 00 00 41 57 41 56 53 48 89 fb 49 be 00 00 00 00 00 fc ff df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 47 83 3b 00 <74> 3a 48 83 c3 48 49 89 df 49 c1 ef 03 43 80 3c 37 00 74 08 48 89
RSP: 0018:ffffc90000007180 EFLAGS: 00000002
RAX: 0000000000000000 RBX: ffffc90000007200 RCX: ffff888021049dc0
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffffc90000007200
RBP: ffffc900000072d0 R08: ffffc90003f7ff58 R09: ffffc90000007250
R10: dffffc0000000000 R11: fffff52000000e4c R12: dffffc0000000000
R13: ffffc90000007200 R14: dffffc0000000000 R15: 1ffff92000000e65
FS:  00007f75d67d76c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000008c00000000 CR3: 000000002abf4000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_callchain_kernel+0x35a/0x760 arch/x86/events/core.c:2784
 get_perf_callchain+0x356/0x460 kernel/events/callchain.c:200
 perf_callchain kernel/events/core.c:7616 [inline]
 perf_prepare_sample+0x352/0x1cb0 kernel/events/core.c:7643
 __perf_event_output kernel/events/core.c:7812 [inline]
 perf_event_output_forward+0x185/0x2e0 kernel/events/core.c:7832
 __perf_event_overflow+0x35f/0x550 kernel/events/core.c:9525
 perf_tp_event+0x324/0xbe0 kernel/events/core.c:10057
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10031
 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 82 fc 9c 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:ffffc90000007b00 EFLAGS: 00000206
RAX: 1fe8678d70b4b500 RBX: 1ffff92000000f64 RCX: 1fe8678d70b4b500
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a4b80
RBP: ffffc90000007bd8 R08: ffffffff902140c7 R09: 1ffffffff2042818
R10: dffffc0000000000 R11: fffffbfff2042819 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]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
 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:format_decode+0xbbb/0x1330 lib/vsprintf.c:2693
Code: 44 24 10 0f b6 04 18 84 c0 0f 85 d9 02 00 00 48 8b 44 24 18 0f b6 04 18 84 c0 0f 85 ea 02 00 00 48 8b 04 24 4c 89 28 49 ff c6 <65> 48 8b 04 25 28 00 00 00 48 3b 44 24 40 0f 85 db 00 00 00 45 29
RSP: 0018:ffffc90003f7e9d0 EFLAGS: 00000293
RAX: ffffffff840c6abb RBX: dffffc0000000000 RCX: ffff888021049dc0
RDX: 0000000000000000 RSI: 0000000000000025 RDI: 0000000000000000
RBP: 0000000000000025 R08: ffff888021049dc0 R09: 0000000000000002
R10: 0000000000000025 R11: 0000000000000000 R12: ffffffff8a2be300
R13: 0000000000000000 R14: ffffffff8a2be301 R15: 0000000000000025
 vsnprintf+0xef/0x1c20 lib/vsprintf.c:2763
 sprintf+0xe4/0x140 lib/vsprintf.c:3013
 print_time kernel/printk/printk.c:1274 [inline]
 info_print_prefix+0x168/0x360 kernel/printk/printk.c:1300
 record_print_text kernel/printk/printk.c:1349 [inline]
 console_unlock+0x650/0x10f0 kernel/printk/printk.c:2725
 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274
 _printk+0xda/0x130 kernel/printk/printk.c:2299
 __nla_validate_parse+0x1f64/0x27b0 lib/nlattr.c:625
 __nla_parse+0x3c/0x50 lib/nlattr.c:710
 __nlmsg_parse include/net/netlink.h:744 [inline]
 nlmsg_parse_deprecated include/net/netlink.h:783 [inline]
 fib_nl_delrule+0x31a/0x1ee0 net/core/fib_rules.c:888
 rtnetlink_rcv_msg+0x7f1/0xf10 net/core/rtnetlink.c:5698
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1090
 call_write_iter include/linux/fs.h:2179 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 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: 0033:0x7f75d857f159
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:00007f75d67d7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f75d8806fa0 RCX: 00007f75d857f159
RDX: 0000000000033fe0 RSI: 0000200000000000 RDI: 0000000000000007
RBP: 00007f75d861606b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f75d8807038 R14: 00007f75d8806fa0 R15: 00007ffe44dba138
 </TASK>
NMI backtrace for cpu 0
CPU: 0 PID: 6252 Comm: syz.2.468 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:perf_output_begin_forward+0x7f/0xa30 kernel/events/ring_buffer.c:270
Code: 5a 65 d8 8b 48 c7 84 24 90 00 00 00 a0 d9 9b 81 4c 8d a4 24 80 00 00 00 49 c1 ec 03 48 b8 f1 f1 f1 f1 f8 f8 f8 f3 4b 89 04 3c <43> c7 44 3c 08 f3 f3 f3 f3 e8 33 49 dd ff 66 43 c7 44 3c 04 00 00
RSP: 0018:ffffc90000007380 EFLAGS: 00000802
RAX: f3f8f8f8f1f1f1f1 RBX: ffff88802b7423d0 RCX: 0000000000000178
RDX: ffff88802b7423d0 RSI: ffffc900000076c0 RDI: ffffc90000007500
RBP: ffffc900000074b0 R08: ffffffff8d8b2bef R09: 1ffffffff1b1657d
R10: dffffc0000000000 R11: fffffbfff1b1657e R12: 1ffff92000000e80
R13: ffffc90000007500 R14: 0000000000000178 R15: dffffc0000000000
FS:  00007f75d67d76c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000008c00000000 CR3: 000000002abf4000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __perf_event_output kernel/events/core.c:7814 [inline]
 perf_event_output_forward+0x19b/0x2e0 kernel/events/core.c:7832
 __perf_event_overflow+0x35f/0x550 kernel/events/core.c:9525
 perf_tp_event+0x324/0xbe0 kernel/events/core.c:10057
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10031
 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 82 fc 9c 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:ffffc90000007b00 EFLAGS: 00000206
RAX: 1fe8678d70b4b500 RBX: 1ffff92000000f64 RCX: 1fe8678d70b4b500
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a4b80
RBP: ffffc90000007bd8 R08: ffffffff902140c7 R09: 1ffffffff2042818
R10: dffffc0000000000 R11: fffffbfff2042819 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]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
 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:format_decode+0xbbb/0x1330 lib/vsprintf.c:2693
Code: 44 24 10 0f b6 04 18 84 c0 0f 85 d9 02 00 00 48 8b 44 24 18 0f b6 04 18 84 c0 0f 85 ea 02 00 00 48 8b 04 24 4c 89 28 49 ff c6 <65> 48 8b 04 25 28 00 00 00 48 3b 44 24 40 0f 85 db 00 00 00 45 29
RSP: 0018:ffffc90003f7e9d0 EFLAGS: 00000293
RAX: ffffffff840c6abb RBX: dffffc0000000000 RCX: ffff888021049dc0
RDX: 0000000000000000 RSI: 0000000000000025 RDI: 0000000000000000
RBP: 0000000000000025 R08: ffff888021049dc0 R09: 0000000000000002
R10: 0000000000000025 R11: 0000000000000000 R12: ffffffff8a2be300
R13: 0000000000000000 R14: ffffffff8a2be301 R15: 0000000000000025
 vsnprintf+0xef/0x1c20 lib/vsprintf.c:2763
 sprintf+0xe4/0x140 lib/vsprintf.c:3013
 print_time kernel/printk/printk.c:1274 [inline]
 info_print_prefix+0x168/0x360 kernel/printk/printk.c:1300
 record_print_text kernel/printk/printk.c:1349 [inline]
 console_unlock+0x650/0x10f0 kernel/printk/printk.c:2725
 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274
 _printk+0xda/0x130 kernel/printk/printk.c:2299
 __nla_validate_parse+0x1f64/0x27b0 lib/nlattr.c:625
 __nla_parse+0x3c/0x50 lib/nlattr.c:710
 __nlmsg_parse include/net/netlink.h:744 [inline]
 nlmsg_parse_deprecated include/net/netlink.h:783 [inline]
 fib_nl_delrule+0x31a/0x1ee0 net/core/fib_rules.c:888
 rtnetlink_rcv_msg+0x7f1/0xf10 net/core/rtnetlink.c:5698
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1090
 call_write_iter include/linux/fs.h:2179 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 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: 0033:0x7f75d857f159
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:00007f75d67d7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f75d8806fa0 RCX: 00007f75d857f159
RDX: 0000000000033fe0 RSI: 0000200000000000 RDI: 0000000000000007
RBP: 00007f75d861606b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f75d8807038 R14: 00007f75d8806fa0 R15: 00007ffe44dba138
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/04 14:51 linux-5.15.y a051a4bf909f 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in fib_nl_delrule
2026/07/06 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.