syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-execprog/4277 is trying to acquire lock:
ffff8880b8f281d8 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2995 [inline]
ffff8880b8f281d8 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3315 [inline]
ffff8880b8f281d8 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x184/0x870 kernel/rcu/tree.c:3406

but task is already holding lock:
ffff8880b8f28418 (&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:3796
       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:1310
       do_initcall_level+0x137/0x1e4 init/main.c:1383
       do_initcalls+0x4b/0x8a init/main.c:1399
       kernel_init_freeable+0x3fa/0x5ac init/main.c:1638
       kernel_init+0x19/0x1b0 init/main.c:1526
       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_5186c38a4019a4cb+0x42/0x46
       bpf_dispatcher_nop_func include/linux/bpf.h:1012 [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:3379
       inet_csk_reset_xmit_timer include/net/inet_connection_sock.h:234 [inline]
       tcp_reset_xmit_timer include/net/tcp.h:1365 [inline]
       tcp_schedule_loss_probe+0x47c/0x8d0 net/ipv4/tcp_output.c:2791
       tcp_write_xmit+0x40da/0x62b0 net/ipv4/tcp_output.c:2740
       __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-execprog/4277:
 #0: ffff888023e10130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1792 [inline]
 #0: ffff888023e10130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: tcp_sendmsg+0x1d/0x40 net/ipv4/tcp.c:1489
 #1: ffff8880b8f28418 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999
 #2: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #2: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #2: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2284 [inline]
 #2: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0xf0/0x400 kernel/trace/bpf_trace.c:2325

stack backtrace:
CPU: 1 PID: 4277 Comm: syz-execprog Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 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_5186c38a4019a4cb+0x42/0x46
 bpf_dispatcher_nop_func include/linux/bpf.h:1012 [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:3379
 inet_csk_reset_xmit_timer include/net/inet_connection_sock.h:234 [inline]
 tcp_reset_xmit_timer include/net/tcp.h:1365 [inline]
 tcp_schedule_loss_probe+0x47c/0x8d0 net/ipv4/tcp_output.c:2791
 tcp_write_xmit+0x40da/0x62b0 net/ipv4/tcp_output.c:2740
 __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: 0033:0x40dd0e
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:000000c003b413e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 000000000040dd0e
RDX: 00000000000004a8 RSI: 000000c006cda5d8 RDI: 0000000000000006
RBP: 000000c003b41428 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 000000c003b41558
R13: 00000000000005f6 R14: 000000c00252f6c0 R15: 000000c006cda000
 </TASK>