======================================================
WARNING: possible circular locking dependency detected
4.19.138-syzkaller #0 Not tainted
------------------------------------------------------
swapper/1/0 is trying to acquire lock:
000000002822fbf5 (&qdisc_tx_lock){+.-.}, at: spin_lock include/linux/spinlock.h:329 [inline]
000000002822fbf5 (&qdisc_tx_lock){+.-.}, at: red_adaptative_timer+0x92/0x5c0 net/sched/sch_red.c:265

but task is already holding lock:
00000000c88aba95 ((&q->adapt_timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:168 [inline]
00000000c88aba95 ((&q->adapt_timer)){+.-.}, at: call_timer_fn+0xc9/0x700 kernel/time/timer.c:1328

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 ((&q->adapt_timer)){+.-.}:
       red_destroy+0x15/0x60 net/sched/sch_red.c:182
       qdisc_destroy+0x180/0x780 net/sched/sch_generic.c:983
       red_change+0x514/0x1080 net/sched/sch_red.c:236
       qdisc_change net/sched/sch_api.c:1239 [inline]
       tc_modify_qdisc+0xf6a/0x1a80 net/sched/sch_api.c:1542
       rtnetlink_rcv_msg+0x453/0xb80 net/core/rtnetlink.c:4778
       netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2455
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x6bb/0xc40 net/netlink/af_netlink.c:1909
       sock_sendmsg_nosec net/socket.c:622 [inline]
       sock_sendmsg+0xc3/0x120 net/socket.c:632
       ___sys_sendmsg+0x7bb/0x8e0 net/socket.c:2115
       __sys_sendmsg net/socket.c:2153 [inline]
       __do_sys_sendmsg net/socket.c:2162 [inline]
       __se_sys_sendmsg net/socket.c:2160 [inline]
       __x64_sys_sendmsg+0x132/0x220 net/socket.c:2160
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&qdisc_tx_lock){+.-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144
       spin_lock include/linux/spinlock.h:329 [inline]
       red_adaptative_timer+0x92/0x5c0 net/sched/sch_red.c:265
       call_timer_fn+0x177/0x700 kernel/time/timer.c:1338
       expire_timers+0x243/0x4e0 kernel/time/timer.c:1375
       __run_timers kernel/time/timer.c:1703 [inline]
       run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1716
       __do_softirq+0x26c/0x9a0 kernel/softirq.c:292
       invoke_softirq kernel/softirq.c:372 [inline]
       irq_exit+0x215/0x260 kernel/softirq.c:412
       exiting_irq arch/x86/include/asm/apic.h:544 [inline]
       smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1094
       apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
       native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
       arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
       default_idle+0x49/0x310 arch/x86/kernel/process.c:557
       cpuidle_idle_call kernel/sched/idle.c:153 [inline]
       do_idle+0x2ec/0x4b0 kernel/sched/idle.c:263
       cpu_startup_entry+0xc5/0xe0 kernel/sched/idle.c:369
       start_secondary+0x41f/0x580 arch/x86/kernel/smpboot.c:271
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((&q->adapt_timer));
                               lock(&qdisc_tx_lock);
                               lock((&q->adapt_timer));
  lock(&qdisc_tx_lock);

 *** DEADLOCK ***

1 lock held by swapper/1/0:
 #0: 00000000c88aba95 ((&q->adapt_timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:168 [inline]
 #0: 00000000c88aba95 ((&q->adapt_timer)){+.-.}, at: call_timer_fn+0xc9/0x700 kernel/time/timer.c:1328

stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.138-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1221
 check_prev_add kernel/locking/lockdep.c:1865 [inline]
 check_prevs_add kernel/locking/lockdep.c:1978 [inline]
 validate_chain kernel/locking/lockdep.c:2419 [inline]
 __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3415
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3907
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144
 spin_lock include/linux/spinlock.h:329 [inline]
 red_adaptative_timer+0x92/0x5c0 net/sched/sch_red.c:265
 call_timer_fn+0x177/0x700 kernel/time/timer.c:1338
 expire_timers+0x243/0x4e0 kernel/time/timer.c:1375
 __run_timers kernel/time/timer.c:1703 [inline]
 run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1716
 __do_softirq+0x26c/0x9a0 kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:372 [inline]
 irq_exit+0x215/0x260 kernel/softirq.c:412
 exiting_irq arch/x86/include/asm/apic.h:544 [inline]
 smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1094
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
 </IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: 48 89 df e8 f4 95 62 fa e9 2e ff ff ff 48 89 df e8 e7 95 62 fa eb 82 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 64 b1 4a 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 54 b1 4a 00 f4 c3 90 90 41 56 41 55
RSP: 0018:ffff8880a9f4fd58 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11a4b6c RBX: dffffc0000000000 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff8880a9f3cc44
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff88d25b50
R13: 1ffff110153e9fb5 R14: 0000000000000000 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
 default_idle+0x49/0x310 arch/x86/kernel/process.c:557
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x2ec/0x4b0 kernel/sched/idle.c:263
 cpu_startup_entry+0xc5/0xe0 kernel/sched/idle.c:369
 start_secondary+0x41f/0x580 arch/x86/kernel/smpboot.c:271
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=15 sclass=netlink_route_socket pid=13801 comm=syz-executor.4
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 296 bytes leftover after parsing attributes in process `syz-executor.4'.
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=103 sclass=netlink_route_socket pid=14058 comm=syz-executor.4
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=103 sclass=netlink_route_socket pid=14060 comm=syz-executor.4
sp0: Synchronizing with TNC
sp0: Synchronizing with TNC