syzbot

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
4 locks held by syz.0.17/4521:
 #0: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
 #1: ffff888020506108 (&sch->q.lock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #1: ffff888020506108 (&sch->q.lock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3924 [inline]
 #1: ffff888020506108 (&sch->q.lock){+...}-{2:2}, at: __dev_queue_xmit+0xa2a/0x2f80 net/core/dev.c:4266
 #2: ffff888020506148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: packet_snd net/packet/af_packet.c:3089 [inline]
 #2: ffff888020506148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: packet_sendmsg+0x3dba/0x5060 net/packet/af_packet.c:3120
 #3: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 4521 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 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
 fq_codel_enqueue+0x105e/0x1600 net/sched/sch_fq_codel.c:243
 qdisc_enqueue include/net/sch_generic.h:842 [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
 packet_snd net/packet/af_packet.c:3089 [inline]
 packet_sendmsg+0x3dba/0x5060 net/packet/af_packet.c:3120
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 ____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2445
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2499
 __sys_sendmsg net/socket.c:2528 [inline]
 __do_sys_sendmsg net/socket.c:2537 [inline]
 __se_sys_sendmsg+0x1af/0x290 net/socket.c:2535
 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: 0033:0x7f70fca46e59
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:00007fffc6028cd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f70fccbffa0 RCX: 00007f70fca46e59
RDX: 0000000000000857 RSI: 0000200000000140 RDI: 0000000000000005
RBP: 00007f70fcadcd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f70fccbffac R14: 00007f70fccbffa0 R15: 00007f70fccbffa0
 </TASK>