====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor/4254 is trying to acquire lock: ffff8880b8e281d8 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2995 [inline] ffff8880b8e281d8 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3315 [inline] ffff8880b8e281d8 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x184/0x870 kernel/rcu/tree.c:3406 but task is already holding lock: ffff8880b8e28418 (&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+0xa4/0xf0 kernel/locking/spinlock.c:162 lock_timer_base+0x123/0x270 kernel/time/timer.c:999 __mod_timer+0x117/0xd20 kernel/time/timer.c:1072 queue_delayed_work_on+0x126/0x1e0 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+0x4cb/0x870 kernel/rcu/tree.c:3432 rtnl_register_internal+0x489/0x590 net/core/rtnetlink.c:260 rtnl_register+0x2e/0x70 net/core/rtnetlink.c:310 ip_rt_init+0x323/0x3b5 net/ipv4/route.c:3792 ip_init+0xa/0x14 net/ipv4/ip_output.c:1771 inet_init+0x2bd/0x3cf net/ipv4/af_inet.c:2033 do_one_initcall+0x214/0x7a0 init/main.c:1298 do_initcall_level+0x137/0x1e4 init/main.c:1371 do_initcalls+0x4b/0x8a init/main.c:1387 kernel_init_freeable+0x3fa/0x5ac init/main.c:1626 kernel_init+0x19/0x1b0 init/main.c:1514 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #0 (krc.lock){..-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662 __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+0x184/0x870 kernel/rcu/tree.c:3406 trie_delete_elem+0x52d/0x690 kernel/bpf/lpm_trie.c:545 bpf_prog_c0188993c79ab9c8+0x3d/0x41 bpf_dispatcher_nop_func include/linux/bpf.h:1001 [inline] __bpf_prog_run include/linux/filter.h:603 [inline] bpf_prog_run include/linux/filter.h:610 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2285 [inline] bpf_trace_run3+0x1e3/0x400 kernel/trace/bpf_trace.c:2325 trace_timer_start include/trace/events/timer.h:53 [inline] enqueue_timer+0x411/0x5c0 kernel/time/timer.c:609 __mod_timer+0x88e/0xd20 kernel/time/timer.c:1113 sk_reset_timer+0x1f/0xb0 net/core/sock.c:3374 tcp_event_new_data_sent+0x20e/0x370 net/ipv4/tcp_output.c:81 tcp_write_xmit+0x1780/0x62b0 net/ipv4/tcp_output.c:2716 __tcp_push_pending_frames+0x93/0x340 net/ipv4/tcp_output.c:2894 tcp_sendmsg_locked+0x3689/0x3f10 net/ipv4/tcp.c:1462 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1490 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] sock_write_iter+0x2b5/0x3a0 net/socket.c:1143 call_write_iter include/linux/fs.h:2265 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x44c/0x960 fs/read_write.c:584 ksys_write+0x143/0x240 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x68/0xd2 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 *** 3 locks held by syz-executor/4254: #0: ffff8880287e19b0 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1756 [inline] #0: ffff8880287e19b0 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_sendmsg+0x1d/0x40 net/ipv4/tcp.c:1489 #1: ffff8880b8e28418 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999 #2: ffffffff8cb2a9e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #2: ffffffff8cb2a9e0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #2: ffffffff8cb2a9e0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2284 [inline] #2: ffffffff8cb2a9e0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0xf0/0x400 kernel/trace/bpf_trace.c:2325 stack backtrace: CPU: 0 PID: 4254 Comm: syz-executor Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025 Call Trace: dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662 __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+0x184/0x870 kernel/rcu/tree.c:3406 trie_delete_elem+0x52d/0x690 kernel/bpf/lpm_trie.c:545 bpf_prog_c0188993c79ab9c8+0x3d/0x41 bpf_dispatcher_nop_func include/linux/bpf.h:1001 [inline] __bpf_prog_run include/linux/filter.h:603 [inline] bpf_prog_run include/linux/filter.h:610 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2285 [inline] bpf_trace_run3+0x1e3/0x400 kernel/trace/bpf_trace.c:2325 trace_timer_start include/trace/events/timer.h:53 [inline] enqueue_timer+0x411/0x5c0 kernel/time/timer.c:609 __mod_timer+0x88e/0xd20 kernel/time/timer.c:1113 sk_reset_timer+0x1f/0xb0 net/core/sock.c:3374 tcp_event_new_data_sent+0x20e/0x370 net/ipv4/tcp_output.c:81 tcp_write_xmit+0x1780/0x62b0 net/ipv4/tcp_output.c:2716 __tcp_push_pending_frames+0x93/0x340 net/ipv4/tcp_output.c:2894 tcp_sendmsg_locked+0x3689/0x3f10 net/ipv4/tcp.c:1462 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1490 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] sock_write_iter+0x2b5/0x3a0 net/socket.c:1143 call_write_iter include/linux/fs.h:2265 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x44c/0x960 fs/read_write.c:584 ksys_write+0x143/0x240 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fc6c5d8d660 Code: 40 00 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d 01 af 20 00 00 74 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 48 89 RSP: 002b:00007ffdab0decd8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000000000ff95b00 RCX: 00007fc6c5d8d660 RDX: 0000000000000160 RSI: 00007fc6bfbffea0 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000007 R09: 00000000003ffde8 R10: 327dccbd1bf6da85 R11: 0000000000000202 R12: 0000000000000160 R13: 000055557682d0a0 R14: 00007ffdab0df1a0 R15: 00007fc6bfbffea0