====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ rcu_preempt/16 is trying to acquire lock: ffff8880b8f28218 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2995 [inline] ffff8880b8f28218 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3315 [inline] ffff8880b8f28218 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x18b/0x890 kernel/rcu/tree.c:3406 but task is already holding lock: ffff8880b8f28458 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&base->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb0/0x100 kernel/locking/spinlock.c:162 lock_timer_base+0x123/0x270 kernel/time/timer.c:999 __mod_timer+0xf9/0xd20 kernel/time/timer.c:1080 queue_delayed_work_on+0x12d/0x1f0 kernel/workqueue.c:1704 queue_delayed_work include/linux/workqueue.h:527 [inline] schedule_delayed_monitor_work kernel/rcu/tree.c:3176 [inline] kvfree_call_rcu+0x4fb/0x890 kernel/rcu/tree.c:3432 rtnl_register_internal+0x485/0x590 net/core/rtnetlink.c:260 rtnl_register+0x2e/0x70 net/core/rtnetlink.c:310 ip_rt_init+0x324/0x3b6 net/ipv4/route.c:3753 ip_init+0xa/0x14 net/ipv4/ip_output.c:1779 inet_init+0x2bd/0x3cf net/ipv4/af_inet.c:2033 do_one_initcall+0x257/0x800 init/main.c:1309 do_initcall_level+0x13d/0x1ed init/main.c:1382 do_initcalls+0x4b/0x8a init/main.c:1398 kernel_init_freeable+0x401/0x5ab init/main.c:1637 kernel_init+0x19/0x1b0 init/main.c:1525 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #0 (krc.lock){..-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 krc_this_cpu_lock kernel/rcu/tree.c:2995 [inline] add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3315 [inline] kvfree_call_rcu+0x18b/0x890 kernel/rcu/tree.c:3406 trie_delete_elem+0x4e9/0x620 kernel/bpf/lpm_trie.c:543 bpf_prog_2c29ac5cdc6b1842+0x3a/0x3e bpf_dispatcher_nop_func include/linux/bpf.h:1012 [inline] __bpf_prog_run include/linux/filter.h:596 [inline] bpf_prog_run include/linux/filter.h:614 [inline] bpf_prog_run_array include/linux/bpf.h:1668 [inline] trace_call_bpf+0x39c/0x6b0 kernel/trace/bpf_trace.c:135 perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:10027 perf_trace_timer_class+0x264/0x2e0 include/trace/events/timer.h:12 trace_timer_cancel include/trace/events/timer.h:138 [inline] debug_deactivate kernel/time/timer.c:832 [inline] detach_timer+0x2c0/0x350 kernel/time/timer.c:878 detach_if_pending kernel/time/timer.c:899 [inline] __try_to_del_timer_sync+0x15c/0x1f0 kernel/time/timer.c:1417 __timer_delete_sync+0x21f/0x2e0 kernel/time/timer.c:1574 timer_delete_sync kernel/time/timer.c:1629 [inline] del_timer_sync include/linux/timer.h:200 [inline] schedule_timeout+0x18e/0x2d0 kernel/time/timer.c:2169 rcu_gp_fqs_loop+0x303/0x1350 kernel/rcu/tree.c:1706 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&base->lock); lock(krc.lock); lock(&base->lock); lock(krc.lock); *** DEADLOCK *** 2 locks held by rcu_preempt/16: #0: ffff8880b8f28458 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999 #1: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #1: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #1: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: trace_call_bpf+0xbf/0x6b0 kernel/trace/bpf_trace.c:134 stack backtrace: CPU: 1 PID: 16 Comm: rcu_preempt Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 Call Trace: dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 krc_this_cpu_lock kernel/rcu/tree.c:2995 [inline] add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3315 [inline] kvfree_call_rcu+0x18b/0x890 kernel/rcu/tree.c:3406 trie_delete_elem+0x4e9/0x620 kernel/bpf/lpm_trie.c:543 bpf_prog_2c29ac5cdc6b1842+0x3a/0x3e bpf_dispatcher_nop_func include/linux/bpf.h:1012 [inline] __bpf_prog_run include/linux/filter.h:596 [inline] bpf_prog_run include/linux/filter.h:614 [inline] bpf_prog_run_array include/linux/bpf.h:1668 [inline] trace_call_bpf+0x39c/0x6b0 kernel/trace/bpf_trace.c:135 perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:10027 perf_trace_timer_class+0x264/0x2e0 include/trace/events/timer.h:12 trace_timer_cancel include/trace/events/timer.h:138 [inline] debug_deactivate kernel/time/timer.c:832 [inline] detach_timer+0x2c0/0x350 kernel/time/timer.c:878 detach_if_pending kernel/time/timer.c:899 [inline] __try_to_del_timer_sync+0x15c/0x1f0 kernel/time/timer.c:1417 __timer_delete_sync+0x21f/0x2e0 kernel/time/timer.c:1574 timer_delete_sync kernel/time/timer.c:1629 [inline] del_timer_sync include/linux/timer.h:200 [inline] schedule_timeout+0x18e/0x2d0 kernel/time/timer.c:2169 rcu_gp_fqs_loop+0x303/0x1350 kernel/rcu/tree.c:1706 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295