syzbot


WARNING: locking bug in __clocksource_register_scale

Status: upstream: reported on 2026/06/20 05:05
Subsystems: kernel
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+433936a09a76cdc554a6@syzkaller.appspotmail.com
First crash: 7d07h, last: 2h14m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
3846ea03-6c42-4371-8f4c-0304fb53518e assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING: locking bug in __clocksource_register_scale 2026/06/18 03:10 2026/06/18 03:10 2026/06/18 04:00 b62b3ded1759f79b37600c5ffe2b0a81b919b0b0

			
		
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[syzbot] [kernel?] WARNING: locking bug in __clocksource_register_scale 1 (2) 2026/06/20 21:47

Sample crash report:
Fallback order for Node 1: 1 0 
Built 2 zonelists, mobility grouping on.  Total pages: 2097051
Policy zone: Normal
mem auto-init: stack:all(zero), heap alloc:on, heap free:off
stackdepot: allocating hash table via alloc_large_system_hash
stackdepot hash table entries: 1048576 (order: 12, 16777216 bytes, linear)
stackdepot: allocating space for 8192 stack pools via memblock
**********************************************************
**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
**                                                      **
** This system shows unhashed kernel memory addresses   **
** via the console, logs, and other interfaces. This    **
** might reduce the security of your system.            **
**                                                      **
** If you see this message and you are not debugging    **
** the kernel, report this immediately to your system   **
** administrator!                                       **
**                                                      **
** Use hash_pointers=always to force this mode off      **
**                                                      **
**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
**********************************************************
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=2
allocated 167772160 bytes of page_ext
Node 0, zone      DMA: page owner found early allocated 0 pages
Node 0, zone    DMA32: page owner found early allocated 21208 pages
Node 0, zone   Normal: page owner found early allocated 43 pages
Node 1, zone   Normal: page owner found early allocated 19848 pages
Kernel/User page tables isolation: enabled
Dynamic Preempt: full
Running RCU self tests
Running RCU synchronous self tests
rcu: Preemptible hierarchical RCU implementation.
rcu: 	RCU lockdep checking is enabled.
rcu: 	RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=2.
rcu: 	RCU callback double-/use-after-free debug is enabled.
rcu: 	RCU_SOFTIRQ processing moved to rcuc kthreads.
rcu: 	RCU debug extended QS entry/exit.
	No expedited grace period (rcu_normal_after_boot).
	Trampoline variant of Tasks RCU enabled.
	Tracing variant of Tasks RCU enabled.
rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies.
rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=2
Running RCU synchronous self tests
RCU Tasks: Setting shift to 1 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=2.
NR_IRQS: 4352, nr_irqs: 440, preallocated irqs: 16
rcu: srcu_init: Setting srcu_struct sizes based on contention.
clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns

=============================
[ BUG: Invalid wait context ]
syzkaller #0 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffffffff8dfee1b8 (clocksource_mutex){....}-{4:4}, at: __clocksource_register_scale+0x921/0xff0 kernel/time/clocksource.c:1319
other info that might help us debug this:
context-{5:5}
1 lock held by swapper/0/0:
 #0: ffffffff997fb9f0 (&tkd->lock){....}-{2:2}, at: class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:572 [inline]
 #0: ffffffff997fb9f0 (&tkd->lock){....}-{2:2}, at: timekeeping_init+0x227/0x390 kernel/time/timekeeping.c:2064
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_lock_invalid_wait_context kernel/locking/lockdep.c:4830 [inline]
 check_wait_context kernel/locking/lockdep.c:4902 [inline]
 __lock_acquire+0xe39/0x2ce0 kernel/locking/lockdep.c:5187
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
 __clocksource_register_scale+0x921/0xff0 kernel/time/clocksource.c:1319
 __clocksource_register include/linux/clocksource.h:273 [inline]
 clocksource_default_clock+0x20/0x40 kernel/time/jiffies.c:68
 timekeeping_init+0x236/0x390 kernel/time/timekeeping.c:2068
 start_kernel+0x1db/0x3e0 init/main.c:1087
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x157
 </TASK>
kfence: initialized - using 2097152 bytes for 255 objects at 0xffff88823be00000-0xffff88823c000000
Console: colour VGA+ 80x25
printk: legacy console [ttyS0] enabled
printk: legacy bootconsole [earlyser0] disabled
Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
... MAX_LOCKDEP_SUBCLASSES:  8
... MAX_LOCK_DEPTH:          48
... MAX_LOCKDEP_KEYS:        8192
... CLASSHASH_SIZE:          4096
... MAX_LOCKDEP_ENTRIES:     1048576
... MAX_LOCKDEP_CHAINS:      1048576
... CHAINHASH_SIZE:          524288
 memory used by lock dependency info: 106625 kB
 memory used for stack traces: 8320 kB
 per task-struct memory footprint: 1920 bytes
ACPI: Core revision 20260408
APIC: Switch to symmetric I/O mode setup
x2apic enabled
APIC: Switched APIC routing to: physical x2apic
..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1
clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1fb63109b96, max_idle_ns: 440795265316 ns
Calibrating delay loop (skipped) preset value.. 4399.99 BogoMIPS (lpj=21999980)
numa_add_cpu cpu 0 node 0: mask now 0
numa_add_cpu cpu 0 node 1: mask now 0
Last level iTLB entries: 4KB 64, 2MB 8, 4MB 8
Last level dTLB entries: 4KB 64, 2MB 32, 4MB 32, 1GB 4
mitigations: Enabled attack vectors: user_kernel, user_user, guest_host, guest_guest, SMT mitigations: auto
Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl
Spectre V2 : Mitigation: IBRS
RETBleed: Mitigation: IBRS
ITS: Mitigation: Aligned branch/return thunks
Spectre V2 : User space: Mitigation: STIBP via prctl
MDS: Mitigation: Clear CPU buffers
TAA: Mitigation: Clear CPU buffers
MMIO Stale Data: Vulnerable: Clear CPU buffers attempted, no microcode
Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization
Spectre V2 : Spectre v2 / SpectreRSB: Filling RSB on context switch and VMEXIT
Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction Barrier
active return thunk: its_return_thunk
Spectre V2 : Spectre BHI mitigation: SW BHB clearing on syscall and VM exit
x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
pid_max: default: 32768 minimum: 301
landlock: Up and running.
Yama: becoming mindful.
TOMOYO Linux initialized
Smack:  Initializing.
Smack:  Netfilter enabled.
Smack:  IPv6 Netfilter enabled.
LSM support for eBPF active
Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes, vmalloc hugepage)
Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes, vmalloc hugepage)
Mount-cache hash table entries: 16384 (order: 5, 131072 bytes, vmalloc)
Mountpoint-cache hash table entries: 16384 (order: 5, 131072 bytes, vmalloc)
VFS: Finished mounting rootfs on nullfs
Running RCU synchronous self tests
Running RCU synchronous self tests
numa_add_cpu cpu 1 node 0: mask now 0-1
numa_add_cpu cpu 1 node 1: mask now 0-1

Crashes (49):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/23 10:26 upstream 502d801f0ab0 5a630be6 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/23 03:21 upstream 1dc18801be29 5a630be6 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/22 06:37 upstream 8cd8cf7a07e5 43bfcdb0 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 15:02 upstream 5b33fc6492a7 b62b3ded .config console log report [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto WARNING: locking bug in __clocksource_register_scale
2026/06/17 09:33 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/17 09:26 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/17 09:01 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:54 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:39 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:37 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:22 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:19 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:15 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:14 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 08:13 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 05:41 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 23:41 upstream 6b5a2b7d9bc1 0e4b3e40 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 23:40 upstream 6b5a2b7d9bc1 0e4b3e40 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:57 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:56 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:56 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:56 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:56 upstream 31e6aeafcdde 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:55 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:55 upstream 31e6aeafcdde 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:55 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:55 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:54 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:54 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:53 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:53 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:52 upstream 31e6aeafcdde 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING: locking bug in __clocksource_register_scale
2026/06/17 09:24 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING: locking bug in __clocksource_register_scale
2026/06/17 09:21 upstream 6b5a2b7d9bc1 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:57 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:55 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:55 upstream 0e0611827f33 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING: locking bug in __clocksource_register_scale
2026/06/22 09:45 upstream ef0c9f75a195 ab2703f0 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING: locking bug in __clocksource_register_scale
2026/06/19 09:57 upstream 9ecfb2f7287a 023e42b5 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 10:49 upstream b1cbabe84ca1 a3998659 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING: locking bug in __clocksource_register_scale
2026/06/18 16:19 upstream e771677c937d a776b0d0 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: locking bug in __clocksource_register_scale
2026/06/17 09:09 bpf 0e0611827f33 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce WARNING: locking bug in __clocksource_register_scale
2026/06/17 05:42 bpf 0e0611827f33 62cc6db3 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce WARNING: locking bug in __clocksource_register_scale
2026/06/18 22:06 linux-next e2cae00c05d1 a776b0d0 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 15:28 linux-next 8d6dbbbe3ba6 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 15:18 linux-next 8d6dbbbe3ba6 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:54 linux-next 8d6dbbbe3ba6 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
2026/06/16 04:53 linux-next 8d6dbbbe3ba6 50bb0618 .config console log report [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING: locking bug in __clocksource_register_scale
* Struck through repros no longer work on HEAD.