device syzkaller0 entered promiscuous mode
=============================
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.0.17/4313:
 #0: ffffffff8c31efc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
 #1: ffff888073965108 (&sch->q.lock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #1: ffff888073965108 (&sch->q.lock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3924 [inline]
 #1: ffff888073965108 (&sch->q.lock){+...}-{2:2}, at: __dev_queue_xmit+0xa2b/0x2e50 net/core/dev.c:4266
 #2: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 4313 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 qdisc_lookup+0xa6/0x640 net/sched/sch_api.c:304
 qdisc_tree_reduce_backlog+0x188/0x480 net/sched/sch_api.c:797
 cake_enqueue+0x5021/0x8270 net/sched/sch_cake.c:1956
 qdisc_enqueue include/net/sch_generic.h:843 [inline]
 multiq_enqueue+0x29f/0x4b0 net/sched/sch_multiq.c:77
 dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3865
 __dev_xmit_skb net/core/dev.c:3949 [inline]
 __dev_queue_xmit+0xbde/0x2e50 net/core/dev.c:4266
 packet_snd net/packet/af_packet.c:3119 [inline]
 packet_sendmsg+0x3b4f/0x4de0 net/packet/af_packet.c:3150
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 __sys_sendto+0x46d/0x620 net/socket.c:2073
 __do_sys_sendto net/socket.c:2085 [inline]
 __se_sys_sendto net/socket.c:2081 [inline]
 __x64_sys_sendto+0xda/0xf0 net/socket.c:2081
 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: 0033:0x7f390c35d159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc7ebab508 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f390c5e4fa0 RCX: 00007f390c35d159
RDX: 0000000000000001 RSI: 0000200000000280 RDI: 0000000000000006
RBP: 00007f390c3f4024 R08: 0000200000000140 R09: 0000000000000014
R10: 0000000000004088 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f390c5e4fac R14: 00007f390c5e4fa0 R15: 00007f390c5e4fa0
 </TASK>