============================= WARNING: suspicious RCU usage 5.15.189-syzkaller #0 Not tainted ----------------------------- net/sched/sch_api.c:304 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 5 locks held by syz.8.610/7452: #0: ffff0000d51b20e0 (&type->s_umount_key#52/1){+.+.}-{3:3}, at: alloc_super+0x1a8/0x824 fs/super.c:229 #1: ffff800014337720 (console_lock){+.+.}-{0:0}, at: console_trylock_spinning+0x18/0x268 kernel/printk/printk.c:1867 #2: ffff800008017b80 ((&q->perturb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline] #2: ffff800008017b80 ((&q->perturb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd0/0x858 kernel/time/timer.c:1441 #3: ffff0000ed415108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #3: ffff0000ed415108 (&sch->q.lock){+.-.}-{2:2}, at: sfq_perturbation+0x110/0x19d4 net/sched/sch_sfq.c:610 #4: ffff800014341360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311 stack backtrace: CPU: 1 PID: 7452 Comm: syz.8.610 Not tainted 5.15.189-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025 Call trace: dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 lockdep_rcu_suspicious+0x140/0x198 kernel/locking/lockdep.c:6574 qdisc_lookup+0xc8/0x64c net/sched/sch_api.c:304 qdisc_tree_reduce_backlog+0x188/0x410 net/sched/sch_api.c:793 sfq_rehash net/sched/sch_sfq.c:598 [inline] sfq_perturbation+0x18a8/0x19d4 net/sched/sch_sfq.c:613 call_timer_fn+0x19c/0x858 kernel/time/timer.c:1451 expire_timers kernel/time/timer.c:1496 [inline] __run_timers+0x46c/0x6c4 kernel/time/timer.c:1767 run_timer_softirq+0xcc/0x114 kernel/time/timer.c:1782 handle_softirqs+0x344/0xbf0 kernel/softirq.c:576 __do_softirq kernel/softirq.c:610 [inline] do_softirq_own_stack include/asm-generic/softirq_stack.h:10 [inline] invoke_softirq kernel/softirq.c:457 [inline] __irq_exit_rcu+0x240/0x440 kernel/softirq.c:659 irq_exit+0x14/0x88 kernel/softirq.c:683 handle_domain_irq+0x14c/0x1fc kernel/irq/irqdesc.c:711 gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:765 call_on_irq_stack+0x24/0x30 arch/arm64/kernel/entry.S:855 do_interrupt_handler+0x6c/0x88 arch/arm64/kernel/entry-common.c:267 el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline] console_unlock+0xc90/0x133c kernel/printk/printk.c:2748 vprintk_emit+0x13c/0x218 kernel/printk/printk.c:2274 vprintk_default+0x54/0x80 kernel/printk/printk.c:2289 vprintk+0x1e8/0x284 kernel/printk/printk_safe.c:45 _printk+0xd0/0x118 kernel/printk/printk.c:2299 f2fs_printk+0x2d8/0x384 fs/f2fs/super.c:263 f2fs_fill_super+0x5bdc/0x5d84 fs/f2fs/super.c:4433 mount_bdev+0x264/0x358 fs/super.c:1400 f2fs_mount+0x44/0x58 fs/f2fs/super.c:4533 legacy_get_tree+0xd4/0x16c fs/fs_context.c:611 vfs_get_tree+0x90/0x274 fs/super.c:1530 do_new_mount+0x228/0x810 fs/namespace.c:3014 path_mount+0x5b4/0x1000 fs/namespace.c:3344 do_mount fs/namespace.c:3357 [inline] __do_sys_mount fs/namespace.c:3565 [inline] __se_sys_mount fs/namespace.c:3542 [inline] __arm64_sys_mount+0x514/0x5e4 fs/namespace.c:3542 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584