=============================
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
14 locks held by syz-executor/4197:
#0: ffffffff8c3a8b90 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:503 [inline]
#0: ffffffff8c3a8b90 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1466 [inline]
#0: ffffffff8c3a8b90 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x22c/0x13f0 kernel/fork.c:1518
#1: ffff88801ad96328 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#1: ffff88801ad96328 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:504 [inline]
#1: ffff88801ad96328 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#1: ffff88801ad96328 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x249/0x13f0 kernel/fork.c:1518
#2: ffff8880244e1628 (&mm->mmap_lock/1){+.+.}-{3:3}, at: mmap_write_lock_nested include/linux/mmap_lock.h:78 [inline]
#2: ffff8880244e1628 (&mm->mmap_lock/1){+.+.}-{3:3}, at: dup_mmap kernel/fork.c:513 [inline]
#2: ffff8880244e1628 (&mm->mmap_lock/1){+.+.}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#2: ffff8880244e1628 (&mm->mmap_lock/1){+.+.}-{3:3}, at: copy_mm+0x34f/0x13f0 kernel/fork.c:1518
#3: ffff888075073678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#3: ffff888075073678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pte_range mm/memory.c:1032 [inline]
#3: ffff888075073678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pmd_range mm/memory.c:1167 [inline]
#3: ffff888075073678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pud_range mm/memory.c:1204 [inline]
#3: ffff888075073678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_p4d_range mm/memory.c:1228 [inline]
#3: ffff888075073678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_page_range+0xebd/0x3230 mm/memory.c:1301
#4: ffff888063ab6078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pte_range mm/memory.c:1039 [inline]
#4: ffff888063ab6078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pmd_range mm/memory.c:1167 [inline]
#4: ffff888063ab6078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pud_range mm/memory.c:1204 [inline]
#4: ffff888063ab6078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_p4d_range mm/memory.c:1228 [inline]
#4: ffff888063ab6078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_page_range+0xfc9/0x3230 mm/memory.c:1301
#5: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#6: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#7: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#8: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#9: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#10: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#11: ffff88805fe81108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#11: ffff88805fe81108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3924 [inline]
#11: ffff88805fe81108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xa2a/0x2f80 net/core/dev.c:4266
#12: ffff88805fe81148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: neigh_hh_output include/net/neighbour.h:493 [inline]
#12: ffff88805fe81148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: neigh_output include/net/neighbour.h:507 [inline]
#12: ffff88805fe81148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: ip_finish_output2+0xc87/0x10a0 net/ipv4/ip_output.c:228
#13: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 1 PID: 4197 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
pfifo_tail_enqueue+0x372/0x4d0 net/sched/sch_fifo.c:54
qdisc_enqueue include/net/sch_generic.h:832 [inline]
netem_dequeue+0xd4c/0x1410 net/sched/sch_netem.c:737
dequeue_skb net/sched/sch_generic.c:295 [inline]
qdisc_restart net/sched/sch_generic.c:400 [inline]
__qdisc_run+0x236/0x1490 net/sched/sch_generic.c:418
__dev_xmit_skb net/core/dev.c:3955 [inline]
__dev_queue_xmit+0xe3d/0x2f80 net/core/dev.c:4266
neigh_hh_output include/net/neighbour.h:493 [inline]
neigh_output include/net/neighbour.h:507 [inline]
ip_finish_output2+0xc87/0x10a0 net/ipv4/ip_output.c:228
NF_HOOK_COND include/linux/netfilter.h:291 [inline]
ip_output+0x2c0/0x3e0 net/ipv4/ip_output.c:434
dst_output include/net/dst.h:452 [inline]
ip_local_out net/ipv4/ip_output.c:126 [inline]
ip_send_skb+0x129/0x1c0 net/ipv4/ip_output.c:1588
ip_push_pending_frames net/ipv4/ip_output.c:1608 [inline]
ip_send_unicast_reply+0xb8b/0x11f0 net/ipv4/ip_output.c:1748
tcp_v4_send_reset+0x137a/0x21a0 net/ipv4/tcp_ipv4.c:831
tcp_v4_rcv+0x25f9/0x2d10 net/ipv4/tcp_ipv4.c:2174
ip_protocol_deliver_rcu+0x3ad/0x770 net/ipv4/ip_input.c:204
ip_local_deliver_finish+0x1d5/0x320 net/ipv4/ip_input.c:231
NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
__netif_receive_skb_one_core net/core/dev.c:5551 [inline]
__netif_receive_skb+0xcc/0x290 net/core/dev.c:5665
process_backlog+0x370/0x790 net/core/dev.c:6542
__napi_poll+0xc0/0x430 net/core/dev.c:7101
napi_poll net/core/dev.c:7168 [inline]
net_rx_action+0x4d4/0xa10 net/core/dev.c:7258
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:copy_present_pte mm/memory.c:-1 [inline]
RIP: 0010:copy_pte_range mm/memory.c:1081 [inline]
RIP: 0010:copy_pmd_range mm/memory.c:1167 [inline]
RIP: 0010:copy_pud_range mm/memory.c:1204 [inline]
RIP: 0010:copy_p4d_range mm/memory.c:1228 [inline]
RIP: 0010:copy_page_range+0x1199/0x3230 mm/memory.c:1301
Code: 38 74 08 48 89 df e8 16 d7 10 00 48 8b 03 48 89 44 24 68 43 80 3c 3c 00 74 08 4c 89 f7 e8 ff d6 10 00 48 8b 44 24 58 4c 8b 28 <48> 8b 7c 24 30 48 8b 74 24 28 4c 89 ea e8 d5 e0 ff ff 48 85 c0 0f
RSP: 0018:ffffc9000345f6a0 EFLAGS: 00000246
RAX: ffff888063ab7768 RBX: ffff888063f8c998 RCX: ffff888079bfbb80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000345f950 R08: ffffea00018e6e87 R09: 1ffffd400031cdd0
R10: dffffc0000000000 R11: fffff9400031cdd1 R12: 1ffff1100c756eed
R13: 80000000639bb007 R14: ffff888063ab7768 R15: dffffc0000000000
dup_mmap kernel/fork.c:615 [inline]
dup_mm kernel/fork.c:1466 [inline]
copy_mm+0xc86/0x13f0 kernel/fork.c:1518
copy_process+0x17eb/0x3e20 kernel/fork.c:2290
kernel_clone+0x23f/0x990 kernel/fork.c:2679
__do_sys_clone kernel/fork.c:2796 [inline]
__se_sys_clone kernel/fork.c:2780 [inline]
__x64_sys_clone+0x19a/0x210 kernel/fork.c:2780
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: 0033:0x7fde99393292
Code: 89 e7 e8 71 8b f7 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 66 89 c5 85 c0 75 3b 64 48 8b 04 25 10 00 00
RSP: 002b:00007fff7185bcb0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fff7185bcb0 RCX: 00007fde99393292
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fff7185be3c R08: 0000000000000000 R09: 0000000000000001
R10: 000055558ff257d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 0000000000017cda R15: 00007fff7185be90
----------------
Code disassembly (best guess):
0: 38 74 08 48 cmp %dh,0x48(%rax,%rcx,1)
4: 89 df mov %ebx,%edi
6: e8 16 d7 10 00 call 0x10d721
b: 48 8b 03 mov (%rbx),%rax
e: 48 89 44 24 68 mov %rax,0x68(%rsp)
13: 43 80 3c 3c 00 cmpb $0x0,(%r12,%r15,1)
18: 74 08 je 0x22
1a: 4c 89 f7 mov %r14,%rdi
1d: e8 ff d6 10 00 call 0x10d721
22: 48 8b 44 24 58 mov 0x58(%rsp),%rax
27: 4c 8b 28 mov (%rax),%r13
* 2a: 48 8b 7c 24 30 mov 0x30(%rsp),%rdi <-- trapping instruction
2f: 48 8b 74 24 28 mov 0x28(%rsp),%rsi
34: 4c 89 ea mov %r13,%rdx
37: e8 d5 e0 ff ff call 0xffffe111
3c: 48 85 c0 test %rax,%rax
3f: 0f .byte 0xf