KCSAN: data-race in number / vsnprintf

Status: moderation: reported on 2026/08/04 15:09
Subsystems: acpica
[Documentation on labels]
Reported-by: syzbot+5a88382d85493a9fee22@syzkaller.appspotmail.com
First crash: 1d22h, last: 1d22h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
194e750c assessment-kcsan 💥 KCSAN: data-race in number / vsnprintf 2026/08/04 15:08 2026/08/04 15:08 2026/08/04 15:08 d4abbeac

Sample crash report:
      osl-1334 os_signal_semaphore   : Signaling semaphore[ffff8881000c3390|1]
==================================================================
BUG: KCSAN: data-race in number / vsnprintf

write to 0xffffffff89405bc0 of 30 bytes by task 3755 on cpu 1:
 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_os_wait_semaphore+0x29e/0x2b0 drivers/acpi/osl.c:1310
 acpi_ut_acquire_mutex+0x242/0x4a0 drivers/acpi/acpica/utmutex.c:241
 acpi_ns_get_node+0x46/0xc0 drivers/acpi/acpica/nsutils.c:721
 acpi_get_handle+0xfd/0x180 drivers/acpi/acpica/nsxfname.c:98
 acpi_has_method+0x46/0x80 drivers/acpi/utils.c:672
 acpi_pci_set_power_state+0x5d/0x190 drivers/pci/pci-acpi.c:1084
 platform_pci_set_power_state drivers/pci/pci.c:1068 [inline]
 pci_power_up+0x40/0x3b0 drivers/pci/pci.c:1306
 pci_pm_power_up_and_verify_state+0x29/0x130 drivers/pci/pci.c:3153
 pci_pm_default_resume_early drivers/pci/pci-driver.c:591 [inline]
 pci_pm_restore_noirq+0x53/0x1b0 drivers/pci/pci-driver.c:1259
 dpm_run_callback+0x53/0x2f0 drivers/base/power/main.c:510
 device_resume_noirq+0x851/0x880 drivers/base/power/main.c:857
 async_resume_noirq+0x2c/0x40 drivers/base/power/main.c:879
 async_run_entry_fn+0x52/0x180 kernel/async.c:129
 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

write to 0xffffffff89405bca of 1 bytes by task 3757 on cpu 0:
 number+0x5c2/0xb80 lib/vsprintf.c:553
 vsnprintf+0x68f/0x8c0 lib/vsprintf.c:2909
 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+0x150/0x200 drivers/acpi/acpica/utdebug.c:171
 acpi_ut_status_exit+0xc1/0x120 drivers/acpi/acpica/utdebug.c:-1
 acpi_ns_get_node+0xa2/0xc0 drivers/acpi/acpica/nsutils.c:-1
 acpi_get_handle+0xfd/0x180 drivers/acpi/acpica/nsxfname.c:98
 acpi_has_method+0x46/0x80 drivers/acpi/utils.c:672
 acpi_pci_set_power_state+0x5d/0x190 drivers/pci/pci-acpi.c:1084
 platform_pci_set_power_state drivers/pci/pci.c:1068 [inline]
 pci_power_up+0x40/0x3b0 drivers/pci/pci.c:1306
 pci_pm_power_up_and_verify_state+0x29/0x130 drivers/pci/pci.c:3153
 pci_pm_default_resume_early drivers/pci/pci-driver.c:591 [inline]
 pci_pm_restore_noirq+0x53/0x1b0 drivers/pci/pci-driver.c:1259
 dpm_run_callback+0x53/0x2f0 drivers/base/power/main.c:510
 device_resume_noirq+0x851/0x880 drivers/base/power/main.c:857
 async_resume_noirq+0x2c/0x40 drivers/base/power/main.c:879
 async_run_entry_fn+0x52/0x180 kernel/async.c:129
 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

value changed: 0x73 -> 0x65

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3757 Comm: kworker/u8:46 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: async async_run_entry_fn

==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/04 15:08 upstream 848acc8ffe1b d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in number / vsnprintf
* Struck through repros no longer work on HEAD.