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 kernel	6				1	180d	180d	0/29	auto-obsoleted due to no activity on 2025/10/11 04:10
upstream	KCSAN: data-race in futex_hash_allocate / futex_hash_allocate (2) kernel	6				1	121d	121d	0/29	auto-obsoleted due to no activity on 2025/12/09 12:22

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BUG: KCSAN: data-race in futex_hash_allocate / futex_hash_allocate

read-write to 0xffff88810c5a74c0 of 8 bytes by task 12336 on cpu 0:
 futex_hash_allocate+0x673/0x9d0 kernel/futex/core.c:1839
 futex_hash_prctl+0xd8/0xf0 kernel/futex/core.c:1958
 __do_sys_prctl kernel/sys.c:2870 [inline]
 __se_sys_prctl+0x914/0x1320 kernel/sys.c:2519
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2519
 x64_sys_call+0x2533/0x3020 arch/x86/include/generated/asm/syscalls_64.h:158
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810c5a74c0 of 8 bytes by task 12335 on cpu 1:
 futex_pivot_pending kernel/futex/core.c:1748 [inline]
 futex_hash_allocate+0x5fa/0x9d0 kernel/futex/core.c:1829
 futex_hash_prctl+0xd8/0xf0 kernel/futex/core.c:1958
 __do_sys_prctl kernel/sys.c:2870 [inline]
 __se_sys_prctl+0x914/0x1320 kernel/sys.c:2519
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2519
 x64_sys_call+0x2533/0x3020 arch/x86/include/generated/asm/syscalls_64.h:158
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88811bf79cc0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12335 Comm: syz.8.2051 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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