============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
ksoftirqd/1/22 is trying to acquire lock:
ffffc900044e10d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c8/0x5a0 kernel/bpf/ringbuf.c:423
but task is already holding lock:
ffffc900051430d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c8/0x5a0 kernel/bpf/ringbuf.c:423
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&rb->spinlock);
lock(&rb->spinlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
4 locks held by ksoftirqd/1/22:
#0: ffffffff8cd2ff40 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2ff40 (rcu_callback){....}-{0:0}, at: rcu_do_batch kernel/rcu/tree.c:2188 [inline]
#0: ffffffff8cd2ff40 (rcu_callback){....}-{0:0}, at: rcu_core+0xc51/0x1720 kernel/rcu/tree.c:2467
#1: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#1: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#1: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2321 [inline]
#1: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0xf4/0x400 kernel/trace/bpf_trace.c:2362
#2: ffffc900051430d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c8/0x5a0 kernel/bpf/ringbuf.c:423
#3: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#3: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#3: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2321 [inline]
#3: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0xde/0x3c0 kernel/trace/bpf_trace.c:2361
stack backtrace:
CPU: 1 PID: 22 Comm: ksoftirqd/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
check_deadlock kernel/locking/lockdep.c:3062 [inline]
validate_chain kernel/locking/lockdep.c:3856 [inline]
__lock_acquire+0x5d40/0x7c80 kernel/locking/lockdep.c:5137
lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa8/0xf0 kernel/locking/spinlock.c:162
__bpf_ringbuf_reserve+0x1c8/0x5a0 kernel/bpf/ringbuf.c:423
____bpf_ringbuf_output kernel/bpf/ringbuf.c:549 [inline]
bpf_ringbuf_output+0x69/0x1e0 kernel/bpf/ringbuf.c:539
bpf_prog_fab844a31c87a330+0x4d/0x51
bpf_dispatcher_nop_func include/linux/bpf.h:1223 [inline]
__bpf_prog_run include/linux/filter.h:612 [inline]
bpf_prog_run include/linux/filter.h:619 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
__bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
trace_contention_end+0xe6/0x110 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x7ec/0x9d0 kernel/locking/qspinlock.c:560
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:586 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x24e/0x2c0 kernel/locking/spinlock_debug.c:115
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0xb4/0xf0 kernel/locking/spinlock.c:162
__bpf_ringbuf_reserve+0x1c8/0x5a0 kernel/bpf/ringbuf.c:423
____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:474 [inline]
bpf_ringbuf_reserve+0x5c/0x70 kernel/bpf/ringbuf.c:466
bpf_prog_fe0ed97373b08409+0x2d/0x4a
bpf_dispatcher_nop_func include/linux/bpf.h:1223 [inline]
__bpf_prog_run include/linux/filter.h:612 [inline]
bpf_prog_run include/linux/filter.h:619 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
bpf_trace_run3+0x1e7/0x400 kernel/trace/bpf_trace.c:2362
__traceiter_kmem_cache_free+0x34/0x50 include/trace/events/kmem.h:114
trace_kmem_cache_free include/trace/events/kmem.h:114 [inline]
kmem_cache_free+0x1e0/0x280 mm/slub.c:3851
rcu_do_batch kernel/rcu/tree.c:2194 [inline]
rcu_core+0xcc4/0x1720 kernel/rcu/tree.c:2467
handle_softirqs+0x280/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0xa1/0xc0 arch/x86/kernel/irq_work.c:17
asm_sysvec_irq_work+0x1a/0x20 arch/x86/include/asm/idtentry.h:723
RIP: 0010:finish_task_switch+0x26a/0x920 kernel/sched/core.c:5254
Code: 0f 84 37 01 00 00 48 85 db 0f 85 56 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 80 74 1b 09 e8 3b a7 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc900001c7bb8 EFLAGS: 00000286
RAX: 09cce29439d96d00 RBX: 0000000000000000 RCX: 09cce29439d96d00
RDX: dffffc0000000000 RSI: ffffffff8aaabca0 RDI: ffffffff8afc72c0
RBP: ffffc900001c7c10 R08: ffffffff8e4a94ef R09: 1ffffffff1c9529d
R10: dffffc0000000000 R11: fffffbfff1c9529e R12: ffff88801be6bc00
R13: dffffc0000000000 R14: ffff888041668000 R15: ffff8880b8f3cf08
context_switch kernel/sched/core.c:5383 [inline]
__schedule+0x14da/0x44d0 kernel/sched/core.c:6699
schedule+0xbd/0x170 kernel/sched/core.c:6773
smpboot_thread_fn+0x710/0xa00 kernel/smpboot.c:160
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
----------------
Code disassembly (best guess):
0: 0f 84 37 01 00 00 je 0x13d
6: 48 85 db test %rbx,%rbx
9: 0f 85 56 01 00 00 jne 0x165
f: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
14: 4c 8b 75 d0 mov -0x30(%rbp),%r14
18: 4c 89 e7 mov %r12,%rdi
1b: e8 80 74 1b 09 call 0x91b74a0
20: e8 3b a7 2f 00 call 0x2fa760
25: fb sti
26: 4c 8b 65 c0 mov -0x40(%rbp),%r12
* 2a: 49 8d bc 24 f8 15 00 lea 0x15f8(%r12),%rdi <-- trapping instruction
31: 00
32: 48 89 f8 mov %rdi,%rax
35: 48 c1 e8 03 shr $0x3,%rax
39: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax
3e: 84 c0 test %al,%al