KCSAN: data-race in futex_hash_allocate / futex_hash

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in futex_hash_allocate / futex_hash_allocate (3) kernel	6				1	186d	186d	0/29	auto-obsoleted due to no activity on 2026/04/08 09:46
upstream	KCSAN: data-race in futex_hash_allocate / futex_hash_allocate kernel	6				1	366d	366d	0/29	auto-obsoleted due to no activity on 2025/10/11 04:10

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BUG: KCSAN: data-race in futex_hash_allocate / futex_hash_allocate

read-write to 0xffff88810005d768 of 8 bytes by task 20201 on cpu 0:
 futex_hash_allocate+0x67a/0x9d0 kernel/futex/core.c:1839
 futex_hash_prctl+0xd9/0xf0 kernel/futex/core.c:1958
 __do_sys_prctl kernel/sys.c:2869 [inline]
 __se_sys_prctl+0xc88/0x12e0 kernel/sys.c:2518
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2518
 x64_sys_call+0x20cf/0x3000 arch/x86/include/generated/asm/syscalls_64.h:158
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810005d768 of 8 bytes by task 20203 on cpu 1:
 futex_pivot_pending kernel/futex/core.c:1748 [inline]
 futex_hash_allocate+0x601/0x9d0 kernel/futex/core.c:1829
 futex_hash_prctl+0xd9/0xf0 kernel/futex/core.c:1958
 __do_sys_prctl kernel/sys.c:2869 [inline]
 __se_sys_prctl+0xc88/0x12e0 kernel/sys.c:2518
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2518
 x64_sys_call+0x20cf/0x3000 arch/x86/include/generated/asm/syscalls_64.h:158
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8881192057c0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 20203 Comm: syz.3.5268 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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