[syzbot] [kernel?] WARNING in futex_hash_allocate

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 06cf61899d64 Merge tag 'x86-urgent-2026-08-08' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10e07fb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=350a93852ac854927f45
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16e18079580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=156bc2c6580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-06cf6189.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0e1bfee0387b/vmlinux-06cf6189.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c8ce37486654/bzImage-06cf6189.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+350a93...@syzkaller.appspotmail.com

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do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff81e25edd>] prepare_to_wait_event+0x8d/0x720 kernel/sched/wait.c:317
WARNING: kernel/sched/core.c:9120 at __might_sleep+0x94/0xc0 kernel/sched/core.c:9120, CPU#0: syz.0.17/5928
Modules linked in:
CPU: 0 UID: 0 PID: 5928 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__might_sleep+0x97/0xc0 kernel/sched/core.c:9120
Code: 8b 94 24 70 18 00 00 48 85 d2 75 14 48 83 c4 08 89 ee 48 89 df 31 d2 5b 5d 41 5c e9 33 fc ff ff 48 8d 3d 2c 23 4f 0f 48 89 d1 <67> 48 0f b9 3a eb db e8 5d 3d a5 00 eb 9f 89 74 24 04 e8 82 3d a5
RSP: 0018:ffffc900037efb88 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: ffffffff8bcfd700 RCX: ffffffff81e25edd
RDX: ffffffff81e25edd RSI: 0000000000000002 RDI: ffffffff9124e750
RBP: 000000000000026f R08: ffffffff81fc6852 R09: 0000000000000000
R10: ffffc900037efd38 R11: 0000000000000000 R12: ffff88802b582540
R13: 0000000000000000 R14: dffffc0000000000 R15: ffffffff8e80ae80
FS: 00007efd31a166c0(0000) GS:ffff8880d5dec000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efd31a15ff8 CR3: 000000001c3ea000 CR4: 0000000000352ef0
Call Trace:
<TASK>
__mutex_lock_common kernel/locking/mutex.c:623 [inline]
__mutex_lock+0x10e/0x1bd0 kernel/locking/mutex.c:821
class_mutex_constructor include/linux/mutex.h:253 [inline]
futex_pivot_pending kernel/futex/core.c:1789 [inline]
futex_hash_allocate+0xd22/0x1120 kernel/futex/core.c:1872
futex_hash_prctl+0x1b8/0x390 kernel/futex/core.c:2027
__do_sys_prctl+0x16dd/0x2270 kernel/sys.c:2885
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efd30b9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007efd31a16028 EFLAGS: 00000246 ORIG_RAX: 000000000000009d
RAX: ffffffffffffffda RBX: 00007efd30e25fa0 RCX: 00007efd30b9e0d9
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 000000000000004e
RBP: 00007efd30c35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efd30e26038 R14: 00007efd30e25fa0 R15: 00007ffc8e6af968
</TASK>
----------------
Code disassembly (best guess):
0: 8b 94 24 70 18 00 00 mov 0x1870(%rsp),%edx
7: 48 85 d2 test %rdx,%rdx
a: 75 14 jne 0x20
c: 48 83 c4 08 add $0x8,%rsp
10: 89 ee mov %ebp,%esi
12: 48 89 df mov %rbx,%rdi
15: 31 d2 xor %edx,%edx
17: 5b pop %rbx
18: 5d pop %rbp
19: 41 5c pop %r12
1b: e9 33 fc ff ff jmp 0xfffffc53
20: 48 8d 3d 2c 23 4f 0f lea 0xf4f232c(%rip),%rdi # 0xf4f2353
27: 48 89 d1 mov %rdx,%rcx
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: eb db jmp 0xc
31: e8 5d 3d a5 00 call 0xa53d93
36: eb 9f jmp 0xffffffd7
38: 89 74 24 04 mov %esi,0x4(%rsp)
3c: e8 .byte 0xe8
3d: 82 (bad)
3e: 3d .byte 0x3d
3f: a5 movsl %ds:(%rsi),%es:(%rdi)


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