Re: [syzbot] [bpf?] inconsistent lock state in bpf_lru_push_free

syzbot
2025-12-22T20:11:19Z

syzbot has found a reproducer for the following issue on:

HEAD commit: 22cc16c04b78 riscv, bpf: Fix incorrect usage of BPF_TRAMP_..
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=106c3db4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a94030c847137a18
dashboard link: https://syzkaller.appspot.com/bug?extid=c69a0a2c816716f1e0d5
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14b4808a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=146c3db4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/43a53493cb5f/disk-22cc16c0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9726fb9e1980/vmlinux-22cc16c0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/efd2bc050ab6/bzImage-22cc16c0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c69a0a2c816716f1e0d5@syzkaller.appspotmail.com

================================
WARNING: inconsistent lock state
syzkaller #0 Not tainted
--------------------------------
inconsistent {INITIAL USE} -> {IN-NMI} usage.
syz.0.140/6455 [HC1[1]:SC0[0]:HE0:SE1] takes:
ffffe8ffffd582d8 (&l->lock#2){....}-{2:2}, at: bpf_lru_push_free+0x13e/0x520 kernel/bpf/bpf_lru_list.c:-1
{INITIAL USE} state was registered at:
lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
bpf_percpu_lru_pop_free kernel/bpf/bpf_lru_list.c:407 [inline]
bpf_lru_pop_free+0xcb/0x19b0 kernel/bpf/bpf_lru_list.c:494
prealloc_lru_pop kernel/bpf/hashtab.c:299 [inline]
htab_lru_map_update_elem+0x168/0x8a0 kernel/bpf/hashtab.c:1215
bpf_map_update_value+0x751/0x920 kernel/bpf/syscall.c:294
generic_map_update_batch+0x5a9/0x810 kernel/bpf/syscall.c:2038
bpf_map_do_batch+0x39b/0x630 kernel/bpf/syscall.c:5647
__sys_bpf+0x690/0x860 kernel/bpf/syscall.c:-1
__do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6272
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
irq event stamp: 19630
hardirqs last enabled at (19629): [<ffffffff8b5b313e>] syscall_enter_from_user_mode include/linux/entry-common.h:108 [inline]
hardirqs last enabled at (19629): [<ffffffff8b5b313e>] do_syscall_64+0xbe/0xf80 arch/x86/entry/syscall_64.c:90
hardirqs last disabled at (19630): [<ffffffff8b5b7058>] exc_debug_kernel+0x68/0x150 arch/x86/kernel/traps.c:1233
softirqs last enabled at (18324): [<ffffffff81858cca>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last enabled at (18324): [<ffffffff81858cca>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last enabled at (18324): [<ffffffff81858cca>] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:723
softirqs last disabled at (18267): [<ffffffff81858cca>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last disabled at (18267): [<ffffffff81858cca>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last disabled at (18267): [<ffffffff81858cca>] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:723

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

CPU0
----
lock(&l->lock#2);
<Interrupt>
lock(&l->lock#2);

*** DEADLOCK ***

no locks held by syz.0.140/6455.

stack backtrace:
CPU: 1 UID: 0 PID: 6455 Comm: syz.0.140 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<#DB>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_usage_bug+0x28b/0x2e0 kernel/locking/lockdep.c:4042
lock_acquire+0x1f8/0x340 kernel/locking/lockdep.c:5859
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
bpf_lru_push_free+0x13e/0x520 kernel/bpf/bpf_lru_list.c:-1
htab_lru_push_free kernel/bpf/hashtab.c:1183 [inline]
htab_lru_map_delete_elem+0x3a3/0x410 kernel/bpf/hashtab.c:1464
bpf_prog_464bc2be3fc7c272+0x43/0x4b
bpf_dispatcher_nop_func include/linux/bpf.h:1378 [inline]
__bpf_prog_run include/linux/filter.h:723 [inline]
bpf_prog_run include/linux/filter.h:730 [inline]
bpf_overflow_handler kernel/events/core.c:10303 [inline]
__perf_event_overflow+0x39c/0xe70 kernel/events/core.c:10402
perf_swevent_overflow kernel/events/core.c:10536 [inline]
perf_swevent_event+0x4f8/0x5e0 kernel/events/core.c:10574
perf_bp_event+0x251/0x300 kernel/events/core.c:11395
hw_breakpoint_handler arch/x86/kernel/hw_breakpoint.c:556 [inline]
hw_breakpoint_exceptions_notify+0x244/0x680 arch/x86/kernel/hw_breakpoint.c:587
notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85
atomic_notifier_call_chain+0xda/0x180 kernel/notifier.c:223
notify_die+0x130/0x180 kernel/notifier.c:588
notify_debug+0x2e/0x50 arch/x86/kernel/traps.c:1208
exc_debug_kernel+0xbe/0x150 arch/x86/kernel/traps.c:1270
asm_exc_debug+0x1e/0x40 arch/x86/include/asm/idtentry.h:654
RIP: 0010:rep_movs_alternative+0x4a/0x90 arch/x86/lib/copy_user_64.S:74
Code: 48 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 e9 8f 48 04 00 48 8b 06 48 89 07 48 8d 47 08 48 83 e0 f8 48
RSP: 0018:ffffc9000b9ffcf8 EFLAGS: 00050202
RAX: 00007ffffffff001 RBX: 0000000000000050 RCX: 000000000000000f
RDX: 0000000000000001 RSI: 0000200000000301 RDI: ffffc9000b9ffda1
RBP: ffffc9000b9ffea8 R08: ffffc9000b9ffdaf R09: 1ffff9200173ffb5
R10: dffffc0000000000 R11: fffff5200173ffb6 R12: 1ffff9200173ffa8
R13: 0000000000000050 R14: ffffc9000b9ffd60 R15: 00002000000002c0
</#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:223 [inline]
copy_from_bpfptr_offset include/linux/bpfptr.h:53 [inline]
copy_from_bpfptr include/linux/bpfptr.h:59 [inline]
__sys_bpf+0x1e3/0x860 kernel/bpf/syscall.c:6137
__do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6272
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdde098f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdde190d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fdde0be5fa0 RCX: 00007fdde098f749
RDX: 0000000000000050 RSI: 00002000000002c0 RDI: 000000000000000a
RBP: 00007fdde0a13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdde0be6038 R14: 00007fdde0be5fa0 R15: 00007ffde82e83d8
</TASK>
----------------
Code disassembly (best guess):
0: 48 04 00 rex.W add $0x0,%al
3: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
a: 00 00 00
d: 0f 1f 00 nopl (%rax)
10: 48 8b 06 mov (%rsi),%rax
13: 48 89 07 mov %rax,(%rdi)
16: 48 83 c6 08 add $0x8,%rsi
1a: 48 83 c7 08 add $0x8,%rdi
1e: 83 e9 08 sub $0x8,%ecx
21: 74 db je 0xfffffffe
23: 83 f9 08 cmp $0x8,%ecx
26: 73 e8 jae 0x10
28: eb c5 jmp 0xffffffef
* 2a: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction
2c: e9 8f 48 04 00 jmp 0x448c0
31: 48 8b 06 mov (%rsi),%rax
34: 48 89 07 mov %rax,(%rdi)
37: 48 8d 47 08 lea 0x8(%rdi),%rax
3b: 48 83 e0 f8 and $0xfffffffffffffff8,%rax
3f: 48 rex.W

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