KCSAN: data-race in string / vsnprintf

Status: moderation: reported on 2026/08/04 14:52
Subsystems: acpica
[Documentation on labels]
Reported-by: syzbot+8f56859639b847933b36@syzkaller.appspotmail.com
First crash: 2d16h, last: 2d16h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
2ccdd2cf assessment-kcsan 💥 KCSAN: data-race in string / vsnprintf 2026/08/04 14:51 2026/08/04 14:51 2026/08/04 14:51 d4abbeac

Sample crash report:
==================================================================
BUG: KCSAN: data-race in string / vsnprintf

write to 0xffffffff89405bc0 of 30 bytes by task 17607 on cpu 0:
 vsnprintf+0x2c0/0x8c0 lib/vsprintf.c:2896
 vsprintf+0x2a/0x40 lib/vsprintf.c:3090
 acpi_os_vprintf drivers/acpi/osl.c:162 [inline]
 acpi_os_printf+0x87/0x200 drivers/acpi/osl.c:153
 acpi_debug_print+0x113/0x200 drivers/acpi/acpica/utdebug.c:158
 acpi_ps_complete_op+0x754/0x780 drivers/acpi/acpica/psobject.c:612
 acpi_ps_parse_loop+0x1104/0x1520 drivers/acpi/acpica/psloop.c:580
 acpi_ps_parse_aml+0x2b0/0xa10 drivers/acpi/acpica/psparse.c:489
 acpi_ps_execute_method+0x4af/0x660 drivers/acpi/acpica/psxface.c:190
 acpi_ns_evaluate+0x8ae/0xac0 drivers/acpi/acpica/nseval.c:205
 acpi_ut_evaluate_object+0xa7/0x420 drivers/acpi/acpica/uteval.c:60
 acpi_rs_get_method_data+0x6d/0x100 drivers/acpi/acpica/rsutils.c:650
 acpi_walk_resources+0x125/0x1c0 drivers/acpi/acpica/rsxface.c:616
 acpi_pci_link_get_current+0x11c/0x200 drivers/acpi/pci_link.c:254
 acpi_pci_link_set+0x390/0x430 drivers/acpi/pci_link.c:360
 acpi_pci_link_allocate drivers/acpi/pci_link.c:582 [inline]
 acpi_pci_link_allocate_irq+0xb52/0xd60 drivers/acpi/pci_link.c:637
 acpi_pci_irq_enable+0x193/0x3d0 drivers/acpi/pci_irq.c:429
 pcibios_enable_device+0x88/0xa0 arch/x86/pci/common.c:699
 do_pci_enable_device+0x152/0x2d0 drivers/pci/pci.c:1998
 pci_enable_device_flags+0x348/0x3a0 drivers/pci/pci.c:2089
 pci_enable_device+0x1a/0xa0 drivers/pci/pci.c:2122
 i801_probe+0x288/0xbf0 drivers/i2c/busses/i2c-i801.c:1573
 local_pci_probe drivers/pci/pci-driver.c:332 [inline]
 local_pci_probe_callback+0x8a/0x110 drivers/pci/pci-driver.c:361
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff89405bc4 of 1 bytes by task 18085 on cpu 1:
 string_nocheck lib/vsprintf.c:648 [inline]
 string+0x13b/0x220 lib/vsprintf.c:730
 vsnprintf+0x543/0x8c0 lib/vsprintf.c:2945
 vscnprintf+0x41/0x90 lib/vsprintf.c:3014
 printk_sprint+0x30/0x2b0 kernel/printk/printk.c:2222
 vprintk_store+0x57b/0x910 kernel/printk/printk.c:2364
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 acpi_os_vprintf include/linux/printk.h:-1 [inline]
 acpi_os_printf+0x11c/0x200 drivers/acpi/osl.c:153
 acpi_debug_print+0x150/0x200 drivers/acpi/acpica/utdebug.c:171
 acpi_ut_status_exit+0xc1/0x120 drivers/acpi/acpica/utdebug.c:-1
 acpi_ut_copy_eobject_to_iobject+0x58a/0x600 drivers/acpi/acpica/utcopy.c:-1
 acpi_evaluate_object+0x2b7/0x800 drivers/acpi/acpica/nsxfeval.c:259
 acpi_execute_simple_method+0x97/0xc0 drivers/acpi/utils.c:684
 acpi_sleep_tts_switch drivers/acpi/sleep.c:40 [inline]
 acpi_pm_start drivers/acpi/sleep.c:532 [inline]
 acpi_suspend_begin+0xfe/0x170 drivers/acpi/sleep.c:586
 platform_suspend_begin kernel/power/suspend.c:312 [inline]
 suspend_devices_and_enter+0x182/0x10d0 kernel/power/suspend.c:517
 enter_state kernel/power/suspend.c:618 [inline]
 pm_suspend+0x541/0x980 kernel/power/suspend.c:644
 state_store+0x1ba/0x220 kernel/power/main.c:819
 kobj_attr_store+0x4a/0x70 lib/kobject.c:840
 sysfs_kf_write+0xfe/0x120 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x1d2/0x2e0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57d/0x990 fs/read_write.c:687
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x74 -> 0x6f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 18085 Comm: syz.6.3570 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/04 14:51 upstream 848acc8ffe1b d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in string / vsnprintf
* Struck through repros no longer work on HEAD.