====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ udevd/5158 is trying to acquire lock: ffff8880b8f29370 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2959 [inline] ffff8880b8f29370 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3368 [inline] ffff8880b8f29370 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x15a/0x780 kernel/rcu/tree.c:3453 but task is already holding lock: ffff8880b8f29598 (&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+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 dsp_cmx_send+0x1ab8/0x1b40 drivers/isdn/mISDN/dsp_cmx.c:1839 call_timer_fn+0x16e/0x530 kernel/time/timer.c:1700 expire_timers kernel/time/timer.c:1751 [inline] __run_timers+0x52d/0x7d0 kernel/time/timer.c:2022 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2035 handle_softirqs+0x280/0x820 kernel/softirq.c:578 __do_softirq kernel/softirq.c:612 [inline] invoke_softirq kernel/softirq.c:452 [inline] __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 kernfs_open_file_mutex_ptr fs/kernfs/file.c:47 [inline] kernfs_deref_open_node_locked fs/kernfs/file.c:111 [inline] kernfs_unlink_open_file+0xa0/0x4c0 fs/kernfs/file.c:634 kernfs_fop_release+0x12e/0x190 fs/kernfs/file.c:825 __fput+0x234/0x970 fs/file_table.c:384 __do_sys_close fs/open.c:1571 [inline] __se_sys_close+0x15f/0x220 fs/open.c:1556 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 *** 5 locks held by udevd/5158: #0: ffff888019e54068 (&kernfs_locks->open_file_mutex[count]){+.+.}-{3:3}, at: kernfs_open_file_mutex_lock fs/kernfs/file.c:56 [inline] #0: ffff888019e54068 (&kernfs_locks->open_file_mutex[count]){+.+.}-{3:3}, at: kernfs_unlink_open_file+0x71/0x4c0 fs/kernfs/file.c:632 #1: ffffc900001f0c00 ((&dsp_spl_tl)){+.-.}-{0:0}, at: call_timer_fn+0xbf/0x530 kernel/time/timer.c:1697 #2: ffffffff8dd22958 (dsp_lock){..-.}-{2:2}, at: dsp_cmx_send+0x26/0x1b40 drivers/isdn/mISDN/dsp_cmx.c:1632 #3: ffff8880b8f29598 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999 #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: __bpf_trace_run kernel/trace/bpf_trace.c:2321 [inline] #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0xf4/0x400 kernel/trace/bpf_trace.c:2362 stack backtrace: CPU: 1 PID: 5158 Comm: udevd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Call Trace: 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 dsp_cmx_send+0x1ab8/0x1b40 drivers/isdn/mISDN/dsp_cmx.c:1839 call_timer_fn+0x16e/0x530 kernel/time/timer.c:1700 expire_timers kernel/time/timer.c:1751 [inline] __run_timers+0x52d/0x7d0 kernel/time/timer.c:2022 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2035 handle_softirqs+0x280/0x820 kernel/softirq.c:578 __do_softirq kernel/softirq.c:612 [inline] invoke_softirq kernel/softirq.c:452 [inline] __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 RIP: 0010:kernfs_open_file_mutex_ptr fs/kernfs/file.c:47 [inline] RIP: 0010:kernfs_deref_open_node_locked fs/kernfs/file.c:111 [inline] RIP: 0010:kernfs_unlink_open_file+0xa0/0x4c0 fs/kernfs/file.c:634 Code: 41 89 c7 31 ff 89 c6 e8 7e f0 72 ff 45 85 ff 74 5d 48 c7 c0 a0 4d f8 96 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <74> 0c 48 c7 c7 a0 4d f8 96 e8 82 46 ca ff 48 8b 05 ab aa e5 14 41 RSP: 0018:ffffc90010bbfdc0 EFLAGS: 00000246 RAX: 1ffffffff2df09b4 RBX: ffff888019e54000 RCX: dffffc0000000000 RDX: ffff88801ae80000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffff8e4a8b6f R09: 1ffffffff1c9516d R10: dffffc0000000000 R11: fffffbfff1c9516e R12: 0000000000000000 R13: ffff888140bb1000 R14: dffffc0000000000 R15: 0000000000000001 kernfs_fop_release+0x12e/0x190 fs/kernfs/file.c:825 __fput+0x234/0x970 fs/file_table.c:384 __do_sys_close fs/open.c:1571 [inline] __se_sys_close+0x15f/0x220 fs/open.c:1556 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: 0033:0x7f8a5a715a67 Code: 44 00 00 48 83 ec 10 48 63 ff 45 31 c9 45 31 c0 6a 01 31 c9 e8 ca 19 f9 ff 48 83 c4 18 c3 0f 1f 44 00 00 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 61 b3 0d 00 f7 d8 64 89 02 b8 RSP: 002b:00007ffeb32e8638 EFLAGS: 00000297 ORIG_RAX: 0000000000000003 RAX: ffffffffffffffda RBX: 00005609ffae67a0 RCX: 00007f8a5a715a67 RDX: 00007f8a5a7efea0 RSI: 00005609ffae8a00 RDI: 000000000000000c RBP: 00007f8a5a7efff0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000000 R13: 00005609d3be5100 R14: 00007ffeb32e89a0 R15: 00007ffeb32e8890 ---------------- Code disassembly (best guess): 0: 41 89 c7 mov %eax,%r15d 3: 31 ff xor %edi,%edi 5: 89 c6 mov %eax,%esi 7: e8 7e f0 72 ff call 0xff72f08a c: 45 85 ff test %r15d,%r15d f: 74 5d je 0x6e 11: 48 c7 c0 a0 4d f8 96 mov $0xffffffff96f84da0,%rax 18: 48 c1 e8 03 shr $0x3,%rax 1c: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx 23: fc ff df 26: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) * 2a: 74 0c je 0x38 <-- trapping instruction 2c: 48 c7 c7 a0 4d f8 96 mov $0xffffffff96f84da0,%rdi 33: e8 82 46 ca ff call 0xffca46ba 38: 48 8b 05 ab aa e5 14 mov 0x14e5aaab(%rip),%rax # 0x14e5aaea 3f: 41 rex.B