============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:4/1209 is trying to acquire lock:
ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3203 [inline]
ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3510 [inline]
ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x18d/0x7d0 kernel/rcu/tree.c:3601

but task is already holding lock:
ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3203 [inline]
ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3510 [inline]
ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x18d/0x7d0 kernel/rcu/tree.c:3601

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

       CPU0
       ----
  lock(krc.lock);
  lock(krc.lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

8 locks held by kworker/u4:4/1209:
 #0: ffff888016dcd938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1
 #1: ffffc90004f97d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285
 #2: ffffffff8d430950 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x148/0xba0 net/core/net_namespace.c:589
 #3: ffffffff8c44d0f8 (sysctl_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #3: ffffffff8c44d0f8 (sysctl_lock){+.+.}-{2:2}, at: start_unregistering fs/proc/proc_sysctl.c:303 [inline]
 #3: ffffffff8c44d0f8 (sysctl_lock){+.+.}-{2:2}, at: drop_sysctl_table+0x1a1/0x4e0 fs/proc/proc_sysctl.c:1681
 #4: ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3203 [inline]
 #4: ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3510 [inline]
 #4: ffff8880b9027eb8 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x18d/0x7d0 kernel/rcu/tree.c:3601
 #5: ffff8880b90280d8 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:946
 #6: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
 #7: ffff88802120f238 (&trie->lock){....}-{2:2}, at: trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467

stack backtrace:
CPU: 0 PID: 1209 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 __lock_acquire+0x1236/0x7d10 kernel/locking/lockdep.c:-1
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 krc_this_cpu_lock kernel/rcu/tree.c:3203 [inline]
 add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3510 [inline]
 kvfree_call_rcu+0x18d/0x7d0 kernel/rcu/tree.c:3601
 trie_delete_elem+0x58c/0x710 kernel/bpf/lpm_trie.c:-1
 bpf_prog_2c29ac5cdc6b1842+0x3a/0x79c
 bpf_dispatcher_nop_func include/linux/bpf.h:888 [inline]
 __bpf_prog_run include/linux/filter.h:628 [inline]
 bpf_prog_run include/linux/filter.h:635 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
 bpf_trace_run3+0x19e/0x350 kernel/trace/bpf_trace.c:1916
 trace_timer_start include/trace/events/timer.h:52 [inline]
 enqueue_timer+0x394/0x520 kernel/time/timer.c:586
 internal_add_timer kernel/time/timer.c:611 [inline]
 __mod_timer+0x911/0xd00 kernel/time/timer.c:1078
 queue_delayed_work_on+0x12d/0x1f0 kernel/workqueue.c:1715
 queue_delayed_work include/linux/workqueue.h:527 [inline]
 schedule_delayed_work include/linux/workqueue.h:631 [inline]
 kvfree_call_rcu+0x4bc/0x7d0 kernel/rcu/tree.c:3629
 drop_sysctl_table+0x359/0x4e0 fs/proc/proc_sysctl.c:1685
 unregister_sysctl_table+0x87/0x130 fs/proc/proc_sysctl.c:1723
 sctp_sysctl_net_unregister+0x58/0x70 net/sctp/sysctl.c:623
 ops_exit_list net/core/net_namespace.c:172 [inline]
 cleanup_net+0x706/0xba0 net/core/net_namespace.c:635
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>