syzbot


INFO: rcu detected stall in tc_modify_qdisc (2)

Status: upstream: reported C repro on 2024/11/08 00:04
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+3e756bb26a645ac581b7@syzkaller.appspotmail.com
First crash: 247d, last: 1d17h
Bug presence (1)
Date Name Commit Repro Result
2024/12/15 upstream (ToT) 2d8308bf5b67 C [report] INFO: rcu detected stall in do_idle
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in tc_modify_qdisc 1 1 23d 23d 0/2 upstream: reported on 2025/06/19 23:42
linux-6.1 INFO: rcu detected stall in tc_modify_qdisc 1 3 363d 401d 0/3 auto-obsoleted due to no activity on 2024/10/23 00:42
upstream INFO: rcu detected stall in tc_modify_qdisc net 1 C done 584 2d14h 1810d 0/29 upstream: reported C repro on 2020/07/29 05:53
linux-5.15 INFO: rcu detected stall in tc_modify_qdisc origin:lts-only 1 C error 7 27d 333d 0/3 upstream: reported C repro on 2024/08/13 15:46
android-6-1 BUG: soft lockup in tc_modify_qdisc 1 C done done 53 593d 624d 0/2 auto-obsoleted due to no activity on 2024/02/06 04:01
android-5-15 BUG: soft lockup in tc_modify_qdisc origin:lts 1 C done done 254 682d 737d 0/2 auto-obsoleted due to no activity on 2023/11/09 01:01
linux-5.15 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 C error 1 771d 771d 0/3 auto-obsoleted due to no activity on 2023/09/11 01:53
linux-6.1 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 C done 1 769d 769d 3/3 fixed on 2023/07/10 11:22
android-5-10 BUG: soft lockup in tc_modify_qdisc 1 C done done 314 683d 737d 0/2 auto-obsoleted due to no activity on 2023/11/07 07:54
Fix bisection attempts (5)
Created Duration User Patch Repo Result
2025/07/06 01:41 2h15m bisect fix linux-6.1.y OK (0) job log log
2025/04/30 06:49 2h03m bisect fix linux-6.1.y OK (0) job log log
2025/03/27 23:48 2h23m bisect fix linux-6.1.y OK (0) job log log
2025/02/23 08:19 1h46m bisect fix linux-6.1.y OK (0) job log log
2025/01/24 04:14 1h42m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (3 ticks this GP) idle=79f4/1/0x4000000000000000 softirq=8823/8823 fqs=0
	(detected by 1, t=10502 jiffies, g=8601, q=251 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4322 Comm: syz-executor851 Not tainted 6.1.140-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:advance_sched+0x1/0x970 net/sched/sch_taprio.c:692
Code: b2 eb b8 e8 c1 17 35 f9 48 8b 1c 24 eb 05 e8 b6 17 35 f9 48 89 df 48 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d e9 d0 82 6e f9 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 68 48 89 fd 49 bd 00 00 00 00
RSP: 0018:ffffc90000007d10 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff88802b74c648 RCX: ffff88802b74bb80
RDX: 0000000000010000 RSI: 0000000000000000 RDI: ffff888079fe4340
RBP: ffffc90000007e98 R08: dffffc0000000000 R09: fffffbfff1bfd006
R10: fffffbfff1bfd006 R11: 1ffffffff1bfd005 R12: ffff888079fe4340
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff110056e98c9
FS:  00007f9418b796c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9419451020 CR3: 0000000073a85000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __run_hrtimer kernel/time/hrtimer.c:1691 [inline]
 __hrtimer_run_queues+0x522/0xc80 kernel/time/hrtimer.c:1755
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1817
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lockdep_unregister_key+0x4c3/0x530 kernel/locking/lockdep.c:6370
Code: 81 86 90 48 c7 c6 e0 90 63 81 e8 88 93 07 00 e8 d3 a6 07 00 e9 86 fc ff ff e8 89 a0 ab 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b eb a1 0f 0b e9 11 ff ff ff 0f 0b e9 5e ff ff ff
RSP: 0018:ffffc90003f06ee0 EFLAGS: 00000246
RAX: bec15163f77bd300 RBX: 0000000000000000 RCX: bec15163f77bd300
RDX: 0000000000000001 RSI: ffffffff8a6c0ce0 RDI: ffffffff8abf1260
RBP: ffffc90003f06fc0 R08: dffffc0000000000 R09: fffffbfff21111a4
R10: fffffbfff21111a4 R11: 1ffffffff21111a3 R12: 0000000000000206
R13: ffff88806495ea99 R14: ffffffff908881a8 R15: 1ffff920007e0de0
 __qdisc_destroy+0x128/0x430 net/sched/sch_generic.c:1078
 taprio_attach+0x26b/0x420 net/sched/sch_taprio.c:1844
 qdisc_graft+0x1165/0x1570 net/sched/sch_api.c:1143
 tc_modify_qdisc+0xe50/0x1be0 net/sched/sch_api.c:1771
 rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6153
 netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2493
 netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
 netlink_unicast+0x74c/0x8c0 net/netlink/af_netlink.c:1337
 netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1859
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x59b/0x970 net/socket.c:2519
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f94193c9329
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 1f 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9418b79218 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f94194531c8 RCX: 00007f94193c9329
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000004
RBP: 00007f94194531c0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 0000200000000780
R13: 00002000000000c0 R14: 00002000000007d0 R15: 00002000000007c0
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g8601 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=2973
rcu: rcu_preempt kthread starved for 10502 jiffies! g8601 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:26784 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10e9/0x40d0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </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: 4322 Comm: syz-executor851 Not tainted 6.1.140-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:87 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x81/0x290 mm/kasan/generic.c:189
Code: 03 4e 8d 14 3b 4d 89 d6 4d 29 ce 49 83 fe 10 7f 26 4d 85 f6 0f 84 39 01 00 00 48 f7 d3 4c 01 db 41 80 39 00 0f 85 c1 01 00 00 <49> ff c1 48 ff c3 75 ee e9 1c 01 00 00 44 89 cb 83 e3 07 0f 84 b5
RSP: 0018:ffffc900000078c0 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffffffffffffffff RCX: ffffffff8162fc96
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff908b8248
RBP: ffffc90000007b30 R08: dffffc0000000000 R09: fffffbfff2117049
R10: fffffbfff211704a R11: 1ffffffff2117049 R12: ffff88802b74bb80
R13: ffff88802b74c602 R14: 0000000000000001 R15: dffffc0000000001
FS:  00007f9418b796c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9419451020 CR3: 0000000073a85000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 __lock_acquire+0xdc6/0x7c50 kernel/locking/lockdep.c:5019
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0x9f/0xe0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1695 [inline]
 __hrtimer_run_queues+0x5e9/0xc80 kernel/time/hrtimer.c:1755
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1817
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lockdep_unregister_key+0x4c3/0x530 kernel/locking/lockdep.c:6370
Code: 81 86 90 48 c7 c6 e0 90 63 81 e8 88 93 07 00 e8 d3 a6 07 00 e9 86 fc ff ff e8 89 a0 ab 08 41 f7 c4 00 02 00 00 74 d1 fb 84 db <75> d0 eb e1 0f 0b eb a1 0f 0b e9 11 ff ff ff 0f 0b e9 5e ff ff ff
RSP: 0018:ffffc90003f06ee0 EFLAGS: 00000246
RAX: bec15163f77bd300 RBX: 0000000000000000 RCX: bec15163f77bd300
RDX: 0000000000000001 RSI: ffffffff8a6c0ce0 RDI: ffffffff8abf1260
RBP: ffffc90003f06fc0 R08: dffffc0000000000 R09: fffffbfff21111a4
R10: fffffbfff21111a4 R11: 1ffffffff21111a3 R12: 0000000000000206
R13: ffff88806495ea99 R14: ffffffff908881a8 R15: 1ffff920007e0de0
 __qdisc_destroy+0x128/0x430 net/sched/sch_generic.c:1078
 taprio_attach+0x26b/0x420 net/sched/sch_taprio.c:1844
 qdisc_graft+0x1165/0x1570 net/sched/sch_api.c:1143
 tc_modify_qdisc+0xe50/0x1be0 net/sched/sch_api.c:1771
 rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6153
 netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2493
 netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
 netlink_unicast+0x74c/0x8c0 net/netlink/af_netlink.c:1337
 netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1859
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x59b/0x970 net/socket.c:2519
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f94193c9329
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 1f 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9418b79218 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f94194531c8 RCX: 00007f94193c9329
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000004
RBP: 00007f94194531c0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 0000200000000780
R13: 00002000000000c0 R14: 00002000000007d0 R15: 00002000000007c0
 </TASK>

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/30 18:45 linux-6.1.y da3c5173c55f 3d2f584d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/12/14 12:35 linux-6.1.y e4d90d63d385 7cbfbb3a .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/06/04 09:48 linux-6.1.y da3c5173c55f a30356b7 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/05/30 14:24 linux-6.1.y da3c5173c55f 3d2f584d .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2024/11/08 00:03 linux-6.1.y 7c15117f9468 867e44df .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in tc_modify_qdisc
2025/07/11 12:21 linux-6.1.y dfc486ec9cce 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: soft lockup in tc_modify_qdisc
* Struck through repros no longer work on HEAD.