CVE-2025-68336 — locking/spinlock/debug: Fix data-race in do_raw_write_lock

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

locking/spinlock/debug: Fix data-race in do_raw_write_lock

KCSAN reports:

BUG: KCSAN: data-race in do_raw_write_lock / do_raw_write_lock

write (marked) to 0xffff800009cf504c of 4 bytes by task 1102 on cpu 1: do_raw_write_lock+0x120/0x204 _raw_write_lock_irq do_exit call_usermodehelper_exec_async ret_from_fork

read to 0xffff800009cf504c of 4 bytes by task 1103 on cpu 0: do_raw_write_lock+0x88/0x204 _raw_write_lock_irq do_exit call_usermodehelper_exec_async ret_from_fork

value changed: 0xffffffff -> 0x00000001

Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 1103 Comm: kworker/u4:1 6.1.111

Commit 1a365e822372 ("locking/spinlock/debug: Fix various data races") has adressed most of these races, but seems to be not consistent/not complete.

>From do_raw_write_lock() only debug_write_lock_after() part has been converted to WRITE_ONCE(), but not debug_write_lock_before() part. Do it now.

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CVE-2025-68336 — locking/spinlock/debug: Fix data-race in do_raw_write_lock