============================= WARNING: suspicious RCU usage 5.15.185-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.3.315/4950: #0: ffff0000d85dee58 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:117 [inline] #0: ffff0000d85dee58 (&mm->mmap_lock){++++}-{3:3}, at: __mm_populate+0x158/0x36c mm/gup.c:1618 #1: ffff8000143311e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311 #2: ffff0000d7325148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: qdisc_run+0x2c/0x1f8 include/net/pkt_sched.h:131 #3: ffff0000d7325108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #3: ffff0000d7325108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x1e4/0x3bc net/sched/sch_generic.c:354 #4: ffff8000143311e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311 stack backtrace: CPU: 1 PID: 4950 Comm: syz.3.315 Not tainted 5.15.185-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 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+0x204/0x4a0 net/sched/sch_api.c:800 cake_dequeue+0x1800/0x3afc net/sched/sch_cake.c:2189 qdisc_peek_dequeued+0x78/0x1ec include/net/sch_generic.h:1115 tbf_dequeue+0x90/0xc5c net/sched/sch_tbf.c:265 dequeue_skb net/sched/sch_generic.c:292 [inline] qdisc_restart net/sched/sch_generic.c:397 [inline] __qdisc_run+0x1bc/0x1170 net/sched/sch_generic.c:415 qdisc_run+0x40/0x1f8 include/net/pkt_sched.h:132 net_tx_action+0x630/0x81c net/core/dev.c:5128 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+0x24/0x4c arch/arm64/kernel/entry.S:899 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_enable arch/arm64/include/asm/irqflags.h:35 [inline] charge_memcg+0x198/0x220 mm/memcontrol.c:6775 __mem_cgroup_charge+0x38/0xb0 mm/memcontrol.c:6801 mem_cgroup_charge include/linux/memcontrol.h:700 [inline] shmem_add_to_page_cache+0x7c4/0x134c mm/shmem.c:718 shmem_getpage_gfp+0x1258/0x1ef0 mm/shmem.c:1940 shmem_fault+0x170/0x430 mm/shmem.c:2118 __do_fault+0x120/0x5d0 mm/memory.c:3928 do_read_fault mm/memory.c:4264 [inline] do_fault mm/memory.c:4392 [inline] handle_pte_fault mm/memory.c:4650 [inline] __handle_mm_fault mm/memory.c:4785 [inline] handle_mm_fault+0x1b4c/0x2950 mm/memory.c:4883 faultin_page mm/gup.c:976 [inline] __get_user_pages+0x3f4/0x9a4 mm/gup.c:1197 populate_vma_page_range+0x1f4/0x284 mm/gup.c:1529 __mm_populate+0x238/0x36c mm/gup.c:1638 mm_populate include/linux/mm.h:2632 [inline] vm_mmap_pgoff+0x1cc/0x284 mm/util.c:556 ksys_mmap_pgoff+0x11c/0x620 mm/mmap.c:1623 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline] __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline] __arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21 __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