====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.182/6554 is trying to acquire lock: ffff8880b8e29370 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2959 [inline] ffff8880b8e29370 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3368 [inline] ffff8880b8e29370 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x15a/0x780 kernel/rcu/tree.c:3453 but task is already holding lock: ffff8880b8e29598 (&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+0xa8/0xf0 kernel/locking/spinlock.c:162 lock_timer_base+0x123/0x270 kernel/time/timer.c:999 __mod_timer+0xf9/0xdb0 kernel/time/timer.c:1080 queue_delayed_work_on+0x12a/0x1e0 kernel/workqueue.c:1987 kvfree_call_rcu+0x541/0x780 kernel/rcu/tree.c:3481 rtnl_register_internal+0x486/0x590 net/core/rtnetlink.c:264 rtnl_register+0x32/0x70 net/core/rtnetlink.c:314 ip_rt_init+0x2ec/0x390 net/ipv4/route.c:3796 ip_init+0xe/0x20 net/ipv4/ip_output.c:1663 inet_init+0x2c1/0x3e0 net/ipv4/af_inet.c:2024 do_one_initcall+0x1fd/0x750 init/main.c:1238 do_initcall_level+0x137/0x1f0 init/main.c:1300 do_initcalls+0x69/0xd0 init/main.c:1316 kernel_init_freeable+0x3d2/0x570 init/main.c:1553 kernel_init+0x1d/0x1c0 init/main.c:1443 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 -> #0 (krc.lock){..-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3869 [inline] __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 krc_this_cpu_lock kernel/rcu/tree.c:2959 [inline] add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3368 [inline] kvfree_call_rcu+0x15a/0x780 kernel/rcu/tree.c:3453 trie_delete_elem+0x535/0x6a0 kernel/bpf/lpm_trie.c:545 bpf_prog_5186c38a4019a4cb+0x4a/0x4e 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 __bpf_trace_timer_start+0x14a/0x1b0 include/trace/events/timer.h:53 __traceiter_timer_start+0x77/0xc0 include/trace/events/timer.h:53 trace_timer_start include/trace/events/timer.h:53 [inline] enqueue_timer+0x398/0x530 kernel/time/timer.c:609 internal_add_timer kernel/time/timer.c:634 [inline] __mod_timer+0x977/0xdb0 kernel/time/timer.c:1131 mrp_join_timer_arm net/802/mrp.c:596 [inline] mrp_join_timer+0x13f/0x170 net/802/mrp.c:611 call_timer_fn+0x16e/0x530 kernel/time/timer.c:1700 expire_timers kernel/time/timer.c:1751 [inline] __run_timers+0x52d/0x7d0 kernel/time/timer.c:2022 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2035 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_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0x56/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 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 *** 4 locks held by syz.3.182/6554: #0: ffffc9000366fb40 ((&app->join_timer)#2){+.-.}-{0:0}, at: call_timer_fn+0xbf/0x530 kernel/time/timer.c:1697 #1: ffff88814ceb3cc8 (&app->lock#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] #1: ffff88814ceb3cc8 (&app->lock#2){+.-.}-{2:2}, at: mrp_join_timer+0xd8/0x170 net/802/mrp.c:609 #2: ffff8880b8e29598 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999 #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_run3+0xf4/0x400 kernel/trace/bpf_trace.c:2362 stack backtrace: CPU: 0 PID: 6554 Comm: syz.3.182 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_noncircular+0x2bd/0x3c0 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3869 [inline] __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 krc_this_cpu_lock kernel/rcu/tree.c:2959 [inline] add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3368 [inline] kvfree_call_rcu+0x15a/0x780 kernel/rcu/tree.c:3453 trie_delete_elem+0x535/0x6a0 kernel/bpf/lpm_trie.c:545 bpf_prog_5186c38a4019a4cb+0x4a/0x4e 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 __bpf_trace_timer_start+0x14a/0x1b0 include/trace/events/timer.h:53 __traceiter_timer_start+0x77/0xc0 include/trace/events/timer.h:53 trace_timer_start include/trace/events/timer.h:53 [inline] enqueue_timer+0x398/0x530 kernel/time/timer.c:609 internal_add_timer kernel/time/timer.c:634 [inline] __mod_timer+0x977/0xdb0 kernel/time/timer.c:1131 mrp_join_timer_arm net/802/mrp.c:596 [inline] mrp_join_timer+0x13f/0x170 net/802/mrp.c:611 call_timer_fn+0x16e/0x530 kernel/time/timer.c:1700 expire_timers kernel/time/timer.c:1751 [inline] __run_timers+0x52d/0x7d0 kernel/time/timer.c:2022 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2035 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_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0x56/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 RIP: 0033:0x7f24a186ed66 Code: 89 fb 48 89 d0 49 8d 14 d2 49 39 50 28 0f 82 b5 03 00 00 c6 44 24 1e 01 45 31 ff 45 31 f6 44 0f b6 e6 85 c0 0f 84 9e 00 00 00 <44> 89 f9 49 8b 50 40 4c 89 f0 49 03 14 ca 80 3d 2d 90 37 00 00 49 RSP: 002b:00007ffda5770bc0 EFLAGS: 00000287 RAX: 000000110c388000 RBX: 00007f24a2715720 RCX: 0000000000000004 RDX: 00000000000015a2 RSI: 0000000000002ad6 RDI: 0000000000000010 RBP: ffffffff813ab5a2 R08: 00007f24a1be6038 R09: 00007f24a1bd2000 R10: 00007f24a13ff008 R11: 000000000000000a R12: 000000000000000a R13: 0000000000000000 R14: ffffffff813ab2d8 R15: 00000000000001f5