=============================
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 syz-executor/4188:
#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: ffff888074662108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#1: ffff888074662108 (&sch->q.lock){+.-.}-{2:2}, at: sfq_perturbation+0x14d/0x20d0 net/sched/sch_sfq.c:610
#2: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 0 PID: 4188 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
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
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:unwind_next_frame+0xc1/0x1d90 arch/x86/kernel/unwind_orc.c:436
Code: 00 4c 89 64 24 58 4c 89 7c 24 48 bf 01 00 00 00 e8 64 53 1d 00 4c 8d 7b 50 4c 89 f8 48 c1 e8 03 48 89 44 24 30 42 80 3c 30 00 <74> 08 4c 89 ff e8 25 1f 89 00 4c 89 7c 24 28 4d 8b 37 4d 85 f6 74
RSP: 0018:ffffc90002f4ee48 EFLAGS: 00000246
RAX: 1ffff920005e9deb RBX: ffffc90002f4ef08 RCX: ffffffff962daf00
RDX: dffffc0000000000 RSI: ffffffff81be278f RDI: ffffffff81350d2c
RBP: ffffc90002f4ef50 R08: ffffc90002f4efd0 R09: 0000000000000001
R10: dffffc0000000000 R11: fffff520005e9ded R12: ffffffff81be278f
R13: ffffc90002f4f290 R14: dffffc0000000000 R15: ffffc90002f4ef58
arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
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]
kfree+0xef/0x2a0 mm/slub.c:4564
xt_free_table_info+0xce/0x190 net/netfilter/x_tables.c:1208
__do_replace+0x7cb/0x9c0 net/ipv6/netfilter/ip6_tables.c:1103
do_replace net/ipv6/netfilter/ip6_tables.c:1160 [inline]
do_ip6t_set_ctl+0xaaa/0xd90 net/ipv6/netfilter/ip6_tables.c:1646
nf_setsockopt+0x25f/0x280 net/netfilter/nf_sockopt.c:101
ipv6_setsockopt+0x2086/0x3cc0 net/ipv6/ipv6_sockglue.c:1014
tcp_setsockopt+0x240/0x1e90 net/ipv4/tcp.c:3722
__sys_setsockopt+0x2bf/0x3d0 net/socket.c:2212
__do_sys_setsockopt net/socket.c:2223 [inline]
__se_sys_setsockopt net/socket.c:2220 [inline]
__x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2220
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: 0033:0x7f9e5ec3e05a
Code: 48 83 ec 10 48 63 c9 48 63 ff 45 89 c9 6a 2c e8 6c 99 fb ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 49 89 ca b8 36 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 06 c3 0f 1f 44 00 00 48 c7 c2 e8 ff ff ff f7
RSP: 002b:00007ffe29f99af8 EFLAGS: 00000202 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007ffe29f99b80 RCX: 00007f9e5ec3e05a
RDX: 0000000000000040 RSI: 0000000000000029 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00000000000003b8 R09: 0000000000000000
R10: 00007f9e5ee87e60 R11: 0000000000000202 R12: 00007f9e5ee87e00
R13: 00007ffe29f99b1c R14: 0000000000000000 R15: 00007f9e5ee89fc0
----------------
Code disassembly (best guess):
0: 00 4c 89 64 add %cl,0x64(%rcx,%rcx,4)
4: 24 58 and $0x58,%al
6: 4c 89 7c 24 48 mov %r15,0x48(%rsp)
b: bf 01 00 00 00 mov $0x1,%edi
10: e8 64 53 1d 00 call 0x1d5379
15: 4c 8d 7b 50 lea 0x50(%rbx),%r15
19: 4c 89 f8 mov %r15,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 89 44 24 30 mov %rax,0x30(%rsp)
25: 42 80 3c 30 00 cmpb $0x0,(%rax,%r14,1)
* 2a: 74 08 je 0x34 <-- trapping instruction
2c: 4c 89 ff mov %r15,%rdi
2f: e8 25 1f 89 00 call 0x891f59
34: 4c 89 7c 24 28 mov %r15,0x28(%rsp)
39: 4d 8b 37 mov (%r15),%r14
3c: 4d 85 f6 test %r14,%r14
3f: 74 .byte 0x74