======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-execprog/5791 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: __mod_timer+0x73b/0xdb0 kernel/time/timer.c:1112

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:1250
       do_initcall_level+0x137/0x1f0 init/main.c:1312
       do_initcalls+0x69/0xd0 init/main.c:1328
       kernel_init_freeable+0x3d2/0x570 init/main.c:1565
       kernel_init+0x1d/0x1c0 init/main.c:1455
       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:1224 [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
       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
       sk_reset_timer+0x23/0xc0 net/core/sock.c:3417
       tcp_ack_snd_check net/ipv4/tcp_input.c:5728 [inline]
       tcp_rcv_established+0xb00/0x1cf0 net/ipv4/tcp_input.c:6174
       tcp_v4_do_rcv+0x4ed/0xb80 net/ipv4/tcp_ipv4.c:1734
       tcp_v4_rcv+0x2334/0x2a50 net/ipv4/tcp_ipv4.c:2166
       ip_protocol_deliver_rcu+0x20e/0x3f0 net/ipv4/ip_input.c:205
       ip_local_deliver_finish+0x2ca/0x510 net/ipv4/ip_input.c:233
       NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
       NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
       __netif_receive_skb_one_core net/core/dev.c:5608 [inline]
       __netif_receive_skb+0xcc/0x290 net/core/dev.c:5722
       process_backlog+0x380/0x6e0 net/core/dev.c:6050
       __napi_poll+0xc0/0x460 net/core/dev.c:6612
       napi_poll net/core/dev.c:6679 [inline]
       net_rx_action+0x5ea/0xbf0 net/core/dev.c:6815
       handle_softirqs+0x280/0x820 kernel/softirq.c:578
       do_softirq+0xed/0x180 kernel/softirq.c:479
       __local_bh_enable_ip+0x178/0x1c0 kernel/softirq.c:406
       local_bh_enable include/linux/bottom_half.h:33 [inline]
       rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline]
       __dev_queue_xmit+0x1449/0x35a0 net/core/dev.c:4452
       dev_queue_xmit include/linux/netdevice.h:3113 [inline]
       neigh_hh_output include/net/neighbour.h:527 [inline]
       neigh_output include/net/neighbour.h:541 [inline]
       ip_finish_output2+0xcd3/0x11d0 net/ipv4/ip_output.c:235
       dst_output include/net/dst.h:467 [inline]
       ip_local_out net/ipv4/ip_output.c:129 [inline]
       __ip_queue_xmit+0x10aa/0x1a10 net/ipv4/ip_output.c:535
       __tcp_transmit_skb+0x1c97/0x32a0 net/ipv4/tcp_output.c:1422
       tcp_transmit_skb net/ipv4/tcp_output.c:1440 [inline]
       tcp_write_xmit+0x174c/0x62e0 net/ipv4/tcp_output.c:2778
       __tcp_push_pending_frames+0x97/0x340 net/ipv4/tcp_output.c:2963
       tcp_sendmsg_locked+0x4286/0x4af0 net/ipv4/tcp.c:1312
       tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1344
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg net/socket.c:745 [inline]
       sock_write_iter+0x2bb/0x3f0 net/socket.c:1160
       call_write_iter include/linux/fs.h:2018 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x43b/0x940 fs/read_write.c:584
       ksys_write+0x147/0x250 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 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 ***

8 locks held by syz-execprog/5791:
 #0: ffff8880786e6130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1767 [inline]
 #0: ffff8880786e6130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: tcp_sendmsg+0x21/0x50 net/ipv4/tcp.c:1343
 #1: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #1: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #1: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: __ip_queue_xmit+0x5c/0x1a10 net/ipv4/ip_output.c:470
 #2: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #2: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #2: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x45c/0x11d0 net/ipv4/ip_output.c:228
 #3: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #3: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #3: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: process_backlog+0x2be/0x6e0 net/core/dev.c:6049
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: ip_local_deliver_finish+0x1cb/0x510 net/ipv4/ip_input.c:232
 #5: ffff88801c3d1930 (slock-AF_INET/1){+.-.}-{2:2}, at: tcp_v4_rcv+0x22d9/0x2a50 net/ipv4/tcp_ipv4.c:2162
 #6: ffff8880b8e29598 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x73b/0xdb0 kernel/time/timer.c:1112
 #7: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #7: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #7: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2321 [inline]
 #7: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0xf4/0x400 kernel/trace/bpf_trace.c:2362

stack backtrace:
CPU: 0 PID: 5791 Comm: syz-execprog Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <IRQ>
 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:1224 [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
 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
 sk_reset_timer+0x23/0xc0 net/core/sock.c:3417
 tcp_ack_snd_check net/ipv4/tcp_input.c:5728 [inline]
 tcp_rcv_established+0xb00/0x1cf0 net/ipv4/tcp_input.c:6174
 tcp_v4_do_rcv+0x4ed/0xb80 net/ipv4/tcp_ipv4.c:1734
 tcp_v4_rcv+0x2334/0x2a50 net/ipv4/tcp_ipv4.c:2166
 ip_protocol_deliver_rcu+0x20e/0x3f0 net/ipv4/ip_input.c:205
 ip_local_deliver_finish+0x2ca/0x510 net/ipv4/ip_input.c:233
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
 __netif_receive_skb_one_core net/core/dev.c:5608 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5722
 process_backlog+0x380/0x6e0 net/core/dev.c:6050
 __napi_poll+0xc0/0x460 net/core/dev.c:6612
 napi_poll net/core/dev.c:6679 [inline]
 net_rx_action+0x5ea/0xbf0 net/core/dev.c:6815
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 do_softirq+0xed/0x180 kernel/softirq.c:479
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x178/0x1c0 kernel/softirq.c:406
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline]
 __dev_queue_xmit+0x1449/0x35a0 net/core/dev.c:4452
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 neigh_hh_output include/net/neighbour.h:527 [inline]
 neigh_output include/net/neighbour.h:541 [inline]
 ip_finish_output2+0xcd3/0x11d0 net/ipv4/ip_output.c:235
 dst_output include/net/dst.h:467 [inline]
 ip_local_out net/ipv4/ip_output.c:129 [inline]
 __ip_queue_xmit+0x10aa/0x1a10 net/ipv4/ip_output.c:535
 __tcp_transmit_skb+0x1c97/0x32a0 net/ipv4/tcp_output.c:1422
 tcp_transmit_skb net/ipv4/tcp_output.c:1440 [inline]
 tcp_write_xmit+0x174c/0x62e0 net/ipv4/tcp_output.c:2778
 __tcp_push_pending_frames+0x97/0x340 net/ipv4/tcp_output.c:2963
 tcp_sendmsg_locked+0x4286/0x4af0 net/ipv4/tcp.c:1312
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1344
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 sock_write_iter+0x2bb/0x3f0 net/socket.c:1160
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x43b/0x940 fs/read_write.c:584
 ksys_write+0x147/0x250 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x40dd0e
Code: 24 28 44 8b 44 24 2c e9 70 ff ff ff cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 49 89 f2 48 89 fa 48 89 ce 48 89 df 0f 05 <48> 3d 01 f0 ff ff 76 15 48 f7 d8 48 89 c1 48 c7 c0 ff ff ff ff 48
RSP: 002b:000000c0009053e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 000000000040dd0e
RDX: 00000000000004a8 RSI: 000000c006b485d8 RDI: 0000000000000006
RBP: 000000c000905428 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 000000c000905558
R13: 00000000000005f6 R14: 000000c00418ca80 R15: 000000c006b48000
 </TASK>