=============================
WARNING: suspicious RCU usage
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
3 locks held by sed/5699:
 #0: ffffc90000007c00 ((&q->perturb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
 #0: ffffc90000007c00 ((&q->perturb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
 #1: ffff88802734d108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #1: ffff88802734d108 (&sch->q.lock){+.-.}-{2:2}, at: sfq_perturbation+0x14d/0x20d0 net/sched/sch_sfq.c:610
 #2: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 5699 Comm: sed Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
 qdisc_tree_reduce_backlog+0x190/0x430 net/sched/sch_api.c:783
 sfq_rehash net/sched/sch_sfq.c:598 [inline]
 sfq_perturbation+0x1f5e/0x20d0 net/sched/sch_sfq.c:613
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:1970
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:core_kernel_text kernel/extable.c:75 [inline]
RIP: 0010:kernel_text_address kernel/extable.c:125 [inline]
RIP: 0010:__kernel_text_address+0x1a/0x100 kernel/extable.c:105
Code: 8d 0f 92 c1 20 c1 0f b6 c1 c3 66 0f 1f 44 00 00 55 41 57 41 56 53 48 81 ff 00 00 00 81 0f 93 c0 48 81 ff cb 7d 00 8a 0f 92 c1 <bb> 01 00 00 00 84 c8 0f 85 a2 00 00 00 49 89 fe 48 c7 c0 c0 c5 89
RSP: 0018:ffffc9000312f660 EFLAGS: 00000287
RAX: 0000000000000001 RBX: ffffc9000312f6f0 RCX: 0000000080000001
RDX: ffffc9000312f601 RSI: ffffc9000312faa8 RDI: ffffffff81bd8a3f
RBP: ffffc9000312f730 R08: ffffc9000312f707 R09: ffffc9000312f6f8
R10: dffffc0000000000 R11: fffff52000625ee1 R12: ffff8880203d9dc0
R13: ffff888061788210 R14: dffffc0000000000 R15: 1ffff92000625ede
 unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
 arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kmem_cache_free+0x8f/0x210 mm/slub.c:3520
 remove_vma mm/mmap.c:188 [inline]
 exit_mmap+0x502/0x640 mm/mmap.c:3227
 __mmput+0x115/0x3b0 kernel/fork.c:1127
 exit_mm+0x588/0x6e0 kernel/exit.c:550
 do_exit+0x5a9/0x20c0 kernel/exit.c:870
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 __do_sys_exit_group kernel/exit.c:1008 [inline]
 __se_sys_exit_group kernel/exit.c:1006 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f80116ac6c5
Code: Unable to access opcode bytes at RIP 0x7f80116ac69b.
RSP: 002b:00007fffcab0d8e8 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f80117adfe8 RCX: 00007f80116ac6c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f80117ac680 R15: 00007f80117ae000
 </TASK>
----------------
Code disassembly (best guess):
   0:	8d 0f                	lea    (%rdi),%ecx
   2:	92                   	xchg   %eax,%edx
   3:	c1 20 c1             	shll   $0xc1,(%rax)
   6:	0f b6 c1             	movzbl %cl,%eax
   9:	c3                   	ret
   a:	66 0f 1f 44 00 00    	nopw   0x0(%rax,%rax,1)
  10:	55                   	push   %rbp
  11:	41 57                	push   %r15
  13:	41 56                	push   %r14
  15:	53                   	push   %rbx
  16:	48 81 ff 00 00 00 81 	cmp    $0xffffffff81000000,%rdi
  1d:	0f 93 c0             	setae  %al
  20:	48 81 ff cb 7d 00 8a 	cmp    $0xffffffff8a007dcb,%rdi
  27:	0f 92 c1             	setb   %cl
* 2a:	bb 01 00 00 00       	mov    $0x1,%ebx <-- trapping instruction
  2f:	84 c8                	test   %cl,%al
  31:	0f 85 a2 00 00 00    	jne    0xd9
  37:	49 89 fe             	mov    %rdi,%r14
  3a:	48                   	rex.W
  3b:	c7                   	.byte 0xc7
  3c:	c0 c0 c5             	rol    $0xc5,%al
  3f:	89                   	.byte 0x89