syzbot

======================================================
WARNING: possible circular locking dependency detected
6.1.119-syzkaller #0 Not tainted
------------------------------------------------------
rcu_preempt/16 is trying to acquire lock:
ffff8880b8e28118 (krc.lock){....}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2991 [inline]
ffff8880b8e28118 (krc.lock){....}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3311 [inline]
ffff8880b8e28118 (krc.lock){....}-{2:2}, at: kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3402

but task is already holding lock:
ffff8880b8e28358 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x120/0x260 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}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
       lock_timer_base+0x120/0x260 kernel/time/timer.c:999
       __mod_timer+0x1cb/0xee0 kernel/time/timer.c:1072
       queue_delayed_work_on+0x156/0x250 kernel/workqueue.c:1704
       queue_delayed_work include/linux/workqueue.h:527 [inline]
       schedule_delayed_monitor_work kernel/rcu/tree.c:3172 [inline]
       kvfree_call_rcu+0x520/0x8c0 kernel/rcu/tree.c:3428
       rtnl_register_internal+0x489/0x580 net/core/rtnetlink.c:260
       rtnl_register+0x32/0x70 net/core/rtnetlink.c:310
       ip_rt_init+0x335/0x3c7 net/ipv4/route.c:3763
       ip_init+0xa/0x14 net/ipv4/ip_output.c:1767
       inet_init+0x2ae/0x3c0 net/ipv4/af_inet.c:2035
       do_one_initcall+0x265/0x8f0 init/main.c:1298
       do_initcall_level+0x157/0x207 init/main.c:1371
       do_initcalls+0x49/0x86 init/main.c:1387
       kernel_init_freeable+0x45c/0x60f init/main.c:1626
       kernel_init+0x19/0x290 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+0x1661/0x5950 kernel/locking/lockdep.c:3825
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
       lock_acquire+0x1f8/0x5a0 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:2991 [inline]
       add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3311 [inline]
       kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3402
       trie_delete_elem+0x53a/0x690 kernel/bpf/lpm_trie.c:532
       bpf_prog_4febba1e7eaf042b+0x42/0x4b
       bpf_dispatcher_nop_func include/linux/bpf.h:989 [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:2271 [inline]
       bpf_trace_run3+0x231/0x440 kernel/trace/bpf_trace.c:2311
       trace_timer_start include/trace/events/timer.h:53 [inline]
       enqueue_timer+0x440/0x600 kernel/time/timer.c:609
       __mod_timer+0x92b/0xee0
       schedule_timeout+0x1b4/0x300 kernel/time/timer.c:1964
       rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
       rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
       kthread+0x28d/0x320 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

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 ***

2 locks held by rcu_preempt/16:
 #0: ffff8880b8e28358 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x120/0x260 kernel/time/timer.c:999
 #1: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #1: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #1: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2270 [inline]
 #1: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0x146/0x440 kernel/trace/bpf_trace.c:2311

stack backtrace:
CPU: 0 PID: 16 Comm: rcu_preempt Not tainted 6.1.119-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2fa/0x3b0 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+0x1661/0x5950 kernel/locking/lockdep.c:3825
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
 lock_acquire+0x1f8/0x5a0 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:2991 [inline]
 add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3311 [inline]
 kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3402
 trie_delete_elem+0x53a/0x690 kernel/bpf/lpm_trie.c:532
 bpf_prog_4febba1e7eaf042b+0x42/0x4b
 bpf_dispatcher_nop_func include/linux/bpf.h:989 [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:2271 [inline]
 bpf_trace_run3+0x231/0x440 kernel/trace/bpf_trace.c:2311
 trace_timer_start include/trace/events/timer.h:53 [inline]
 enqueue_timer+0x440/0x600 kernel/time/timer.c:609
 __mod_timer+0x92b/0xee0
 schedule_timeout+0x1b4/0x300 kernel/time/timer.c:1964
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>