====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ dhcpcd/4326 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+0x186/0x7c0 kernel/rcu/tree.c:3601 but task is already holding lock: ffff88807d461a38 (&trie->lock){....}-{2:2}, at: trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&trie->lock){....}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467 bpf_prog_0c1927fb2cdcb045+0x9f5/0xe6c 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+0x17e/0x320 kernel/trace/bpf_trace.c:1916 __traceiter_timer_start+0x73/0xc0 include/trace/events/timer.h:52 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+0x8e1/0xd20 kernel/time/timer.c:1062 sk_reset_timer+0x1f/0xb0 net/core/sock.c:3137 tipc_sk_finish_conn+0x154/0x7e0 net/tipc/socket.c:1675 tipc_socketpair+0x250/0x470 net/tipc/socket.c:3348 __sys_socketpair+0x2ac/0x540 net/socket.c:1659 __do_sys_socketpair net/socket.c:1695 [inline] __se_sys_socketpair net/socket.c:1692 [inline] __x64_sys_socketpair+0x97/0xb0 net/socket.c:1692 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #1 (&base->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 lock_timer_base+0x123/0x270 kernel/time/timer.c:946 __mod_timer+0x117/0xd20 kernel/time/timer.c:1019 queue_delayed_work_on+0x126/0x1e0 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+0x4a9/0x7c0 kernel/rcu/tree.c:3629 rtnl_register_internal+0x44e/0x540 net/core/rtnetlink.c:223 rtnl_register+0x2e/0x70 net/core/rtnetlink.c:273 ip_rt_init+0x2e0/0x3a0 net/ipv4/route.c:3798 ip_init+0xa/0x20 net/ipv4/ip_output.c:1749 inet_init+0x28b/0x3a0 net/ipv4/af_inet.c:2007 do_one_initcall+0x1ee/0x680 init/main.c:1302 do_initcall_level+0x137/0x1f0 init/main.c:1375 do_initcalls+0x4b/0x90 init/main.c:1391 kernel_init_freeable+0x3ce/0x560 init/main.c:1615 kernel_init+0x19/0x1b0 init/main.c:1506 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #0 (krc.lock){..-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 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+0x186/0x7c0 kernel/rcu/tree.c:3601 trie_delete_elem+0x58c/0x710 kernel/bpf/lpm_trie.c:-1 bpf_prog_f22fcc2a98ec18e8+0x3d/0x1c0 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+0x17e/0x320 kernel/trace/bpf_trace.c:1916 __bpf_trace_kmem_cache_free+0x99/0xc0 include/trace/events/kmem.h:138 __traceiter_kmem_cache_free+0x30/0x50 include/trace/events/kmem.h:138 trace_kmem_cache_free include/trace/events/kmem.h:138 [inline] kmem_cache_free+0x1e7/0x210 mm/slub.c:3521 anon_vma_chain_free mm/rmap.c:143 [inline] unlink_anon_vmas+0x2c8/0x660 mm/rmap.c:417 free_pgtables+0x177/0x2a0 mm/memory.c:426 exit_mmap+0x39e/0x5f0 mm/mmap.c:3217 __mmput+0x115/0x3b0 kernel/fork.c:1127 exit_mm+0x567/0x6c0 kernel/exit.c:550 do_exit+0x5a1/0x20a0 kernel/exit.c:870 do_group_exit+0x12e/0x300 kernel/exit.c:997 __do_sys_exit_group kernel/exit.c:1008 [inline] __se_sys_exit_group kernel/exit.c:1006 [inline] __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 other info that might help us debug this: Chain exists of: krc.lock --> &base->lock --> &trie->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&trie->lock); lock(&base->lock); lock(&trie->lock); lock(krc.lock); *** DEADLOCK *** 3 locks held by dhcpcd/4326: #0: ffff88802ab705c8 (&anon_vma->rwsem){++++}-{3:3}, at: lock_anon_vma_root mm/rmap.c:247 [inline] #0: ffff88802ab705c8 (&anon_vma->rwsem){++++}-{3:3}, at: unlink_anon_vmas+0xfc/0x660 mm/rmap.c:404 #1: ffffffff8c11c660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 #2: ffff88807d461a38 (&trie->lock){....}-{2:2}, at: trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467 stack backtrace: CPU: 0 PID: 4326 Comm: dhcpcd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 Call Trace: dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 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+0x186/0x7c0 kernel/rcu/tree.c:3601 trie_delete_elem+0x58c/0x710 kernel/bpf/lpm_trie.c:-1 bpf_prog_f22fcc2a98ec18e8+0x3d/0x1c0 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+0x17e/0x320 kernel/trace/bpf_trace.c:1916 __bpf_trace_kmem_cache_free+0x99/0xc0 include/trace/events/kmem.h:138 __traceiter_kmem_cache_free+0x30/0x50 include/trace/events/kmem.h:138 trace_kmem_cache_free include/trace/events/kmem.h:138 [inline] kmem_cache_free+0x1e7/0x210 mm/slub.c:3521 anon_vma_chain_free mm/rmap.c:143 [inline] unlink_anon_vmas+0x2c8/0x660 mm/rmap.c:417 free_pgtables+0x177/0x2a0 mm/memory.c:426 exit_mmap+0x39e/0x5f0 mm/mmap.c:3217 __mmput+0x115/0x3b0 kernel/fork.c:1127 exit_mm+0x567/0x6c0 kernel/exit.c:550 do_exit+0x5a1/0x20a0 kernel/exit.c:870 do_group_exit+0x12e/0x300 kernel/exit.c:997 __do_sys_exit_group kernel/exit.c:1008 [inline] __se_sys_exit_group kernel/exit.c:1006 [inline] __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7fa22c9fa6c5 Code: Unable to access opcode bytes at RIP 0x7fa22c9fa69b. RSP: 002b:00007fff40b7b878 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fa22c9fa6c5 RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000001 RBP: 00007fff40b7be88 R08: 0000559019b8d2c0 R09: 0000000000000002 R10: 00000000000000e0 R11: 0000000000000206 R12: 00007fff40b7b8c0 R13: 0000559019b8e950 R14: 00007fff40b7bb00 R15: 00007fff40b7b8b0