[syzbot] [fs?] inconsistent lock state in rht_lock

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0ce37745d4bf Merge tag 'block-7.2-20260724' of git://git.k..
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=145c3fde580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4e38b15c29e6a1d9
dashboard link: https://syzkaller.appspot.com/bug?extid=2fb31ade2d0e920fea9a
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10d872ea580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14aea499580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/570b0c02ea7a/disk-0ce37745.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8b5239f2d447/vmlinux-0ce37745.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dbc5fdc8b45c/bzImage-0ce37745.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2fb31a...@syzkaller.appspotmail.com

================================
WARNING: inconsistent lock state
syzkaller #0 Not tainted
--------------------------------
inconsistent {INITIAL USE} -> {IN-NMI} usage.
syz.2.555/6556 [HC1[1]:SC0[0]:HE0:SE1] takes:
ffff88807fed6838 (rhashtable_bucket){..-.}-{0:0}, at: rht_lock+0x8b/0x180 include/linux/rhashtable.h:331
{INITIAL USE} state was registered at:
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
rht_lock+0xa3/0x180 include/linux/rhashtable.h:331
__rhashtable_insert_fast include/linux/rhashtable.h:784 [inline]
rhashtable_insert_fast include/linux/rhashtable.h:887 [inline]
pidfs_add_pid+0x325/0xc50 fs/pidfs.c:178
alloc_pid+0xe7a/0x1310 kernel/pid.c:338
copy_process+0x20ea/0x4390 kernel/fork.c:2305
kernel_clone+0x2d7/0x940 kernel/fork.c:2748
user_mode_thread+0x110/0x180 kernel/fork.c:2824
rest_init+0x23/0x300 init/main.c:682
start_kernel+0x392/0x3e0 init/main.c:1175
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x157
irq event stamp: 1488
hardirqs last enabled at (1487): [<ffffffff8bd0ce38>] irqentry_exit_to_kernel_mode_after_preempt include/linux/irq-entry-common.h:507 [inline]
hardirqs last enabled at (1487): [<ffffffff8bd0ce38>] irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:542 [inline]
hardirqs last enabled at (1487): [<ffffffff8bd0ce38>] irqentry_exit+0x218/0x8f0 kernel/entry/common.c:167
hardirqs last disabled at (1488): [<ffffffff8bd082f0>] exc_debug_kernel+0x60/0x140 arch/x86/kernel/traps.c:1235
softirqs last enabled at (1442): [<ffffffff81d9b01f>] bpf_prog_load+0x166f/0x1c00 kernel/bpf/syscall.c:3223
softirqs last disabled at (1440): [<ffffffff81d742ec>] spin_lock_bh include/linux/spinlock.h:348 [inline]
softirqs last disabled at (1440): [<ffffffff81d742ec>] bpf_ksym_add+0x2c/0x340 kernel/bpf/core.c:641

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(rhashtable_bucket);
<Interrupt>
lock(rhashtable_bucket);

*** DEADLOCK ***

no locks held by syz.2.555/6556.

stack backtrace:
CPU: 1 UID: 0 PID: 6556 Comm: syz.2.555 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<#DB>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_usage_bug+0x28b/0x2e0 kernel/locking/lockdep.c:4042
lock_acquire+0x1cc/0x350 kernel/locking/lockdep.c:5859
rht_lock+0xa3/0x180 include/linux/rhashtable.h:331
__rhashtable_remove_fast_one include/linux/rhashtable.h:1065 [inline]
__rhashtable_remove_fast include/linux/rhashtable.h:1146 [inline]
rhashtable_remove_fast include/linux/rhashtable.h:1175 [inline]
rhtab_delete_elem+0x404/0x1b30 kernel/bpf/hashtab.c:2954
rhtab_map_delete_elem+0xe2/0x190 kernel/bpf/hashtab.c:2985
bpf_prog_a4f1e23443ac9f8e+0x4e/0x56
bpf_dispatcher_nop_func include/linux/bpf.h:1454 [inline]
__bpf_prog_run include/linux/filter.h:724 [inline]
bpf_prog_run include/linux/filter.h:731 [inline]
bpf_overflow_handler kernel/events/core.c:10671 [inline]
__perf_event_overflow+0x3b9/0xea0 kernel/events/core.c:10770
perf_swevent_overflow kernel/events/core.c:10911 [inline]
perf_swevent_event+0x439/0x810 kernel/events/core.c:-1
perf_bp_event+0x318/0x430 kernel/events/core.c:11812
hw_breakpoint_handler arch/x86/kernel/hw_breakpoint.c:556 [inline]
hw_breakpoint_exceptions_notify+0x243/0x680 arch/x86/kernel/hw_breakpoint.c:587
notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
atomic_notifier_call_chain+0xda/0x180 kernel/notifier.c:223
notify_die+0x144/0x1a0 kernel/notifier.c:588
notify_debug+0x2e/0x50 arch/x86/kernel/traps.c:1210
exc_debug_kernel+0xb1/0x140 arch/x86/kernel/traps.c:1272
asm_exc_debug+0x1e/0x40 arch/x86/include/asm/idtentry.h:631
RIP: 0010:rep_movs_alternative+0x4a/0xa0 arch/x86/lib/copy_user_64.S:74
Code: 61 04 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08 73 e8 eb c5 <f3> a4 c3 cc cc cc cc 48 8b 06 48 89 07 48 8d 47 08 48 83 e0 f8 48
RSP: 0018:ffffc900036efc18 EFLAGS: 00050246
RAX: 00007ffffffff001 RBX: 0000000000000040 RCX: 000000000000003d
RDX: 0000000000000001 RSI: 0000200000000303 RDI: ffffc900036efd53
RBP: ffffc900036efea0 R08: ffffc900036efd8f R09: 1ffff920006ddfb1
R10: dffffc0000000000 R11: fffff520006ddfb2 R12: 1ffff920006ddf94
R13: ffffc900036efd50 R14: ffffc900036efd50 R15: 0000200000000300
</#DB>
<TASK>
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_from_user arch/x86/include/asm/uaccess_64.h:141 [inline]
_inline_copy_from_user include/linux/uaccess.h:185 [inline]
_copy_from_user+0x7a/0xb0 lib/usercopy.c:18
copy_from_user include/linux/uaccess.h:222 [inline]
copy_from_bpfptr_offset include/linux/bpfptr.h:53 [inline]
copy_from_bpfptr include/linux/bpfptr.h:59 [inline]
__sys_bpf+0x2e7/0xd90 kernel/bpf/syscall.c:6370
__do_sys_bpf kernel/bpf/syscall.c:6537 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6534 [inline]
__x64_sys_bpf+0xba/0xd0 kernel/bpf/syscall.c:6534
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f55c159de99
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:00007ffe0f3ce588 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f55c1825fa0 RCX: 00007f55c159de99
RDX: 0000000000000040 RSI: 0000200000000300 RDI: 0000000000000010
RBP: 00007f55c1633eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f55c1825fac R14: 00007f55c1825fa0 R15: 00007f55c1825fa0
</TASK>
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 04 00 add $0x0,%al
2: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
9: 00 00 00
c: 0f 1f 00 nopl (%rax)
f: 48 8b 06 mov (%rsi),%rax
12: 48 89 07 mov %rax,(%rdi)
15: 48 83 c6 08 add $0x8,%rsi
19: 48 83 c7 08 add $0x8,%rdi
1d: 83 e9 08 sub $0x8,%ecx
20: 74 db je 0xfffffffd
22: 83 f9 08 cmp $0x8,%ecx
25: 73 e8 jae 0xf
27: eb c5 jmp 0xffffffee
* 29: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction
2b: c3 ret
2c: cc int3
2d: cc int3
2e: cc int3
2f: cc int3
30: 48 8b 06 mov (%rsi),%rax
33: 48 89 07 mov %rax,(%rdi)
36: 48 8d 47 08 lea 0x8(%rdi),%rax
3a: 48 83 e0 f8 and $0xfffffffffffffff8,%rax
3e: 48 rex.W


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup