syzkaller0: entered promiscuous mode syzkaller0: entered allmulticast mode ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.0.2121/11217 is trying to acquire lock: ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3918 [inline] ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: __dev_queue_xmit+0xb01/0x3640 net/core/dev.c:4434 but task is already holding lock: ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3918 [inline] ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: __dev_queue_xmit+0xb01/0x3640 net/core/dev.c:4434 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&sch->root_lock_key#70); lock(&sch->root_lock_key#70); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by syz.0.2121/11217: #0: ffffffff8d131e00 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #0: ffffffff8d131e00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:838 [inline] #0: ffffffff8d131e00 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x275/0x3640 net/core/dev.c:4393 #1: ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] #1: ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3918 [inline] #1: ffff888077624108 (&sch->root_lock_key#70){+...}-{2:2}, at: __dev_queue_xmit+0xb01/0x3640 net/core/dev.c:4434 #2: ffffffff8d131e00 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #2: ffffffff8d131e00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:838 [inline] #2: ffffffff8d131e00 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x275/0x3640 net/core/dev.c:4393 stack backtrace: CPU: 0 PID: 11217 Comm: syz.0.2121 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106 check_deadlock kernel/locking/lockdep.c:3062 [inline] validate_chain kernel/locking/lockdep.c:3856 [inline] __lock_acquire+0x6809/0x7d80 kernel/locking/lockdep.c:5137 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:3918 [inline] __dev_queue_xmit+0xb01/0x3640 net/core/dev.c:4434 sch_frag_xmit_hook+0x2a8/0x11d0 net/sched/sch_frag.c:148 tcf_mirred_forward net/sched/act_mirred.c:215 [inline] tcf_mirred_to_dev net/sched/act_mirred.c:-1 [inline] tcf_mirred_act+0xbd6/0x1350 net/sched/act_mirred.c:337 tc_act include/net/tc_wrapper.h:221 [inline] tcf_action_exec+0x1a9/0x5d0 net/sched/act_api.c:1097 tcf_exts_exec include/net/pkt_cls.h:363 [inline] basic_classify+0x1b2/0x2d0 net/sched/cls_basic.c:54 tc_classify include/net/tc_wrapper.h:227 [inline] __tcf_classify net/sched/cls_api.c:1754 [inline] tcf_classify+0x421/0xfc0 net/sched/cls_api.c:1850 qfq_classify net/sched/sch_qfq.c:715 [inline] qfq_enqueue+0x320/0x12e0 net/sched/sch_qfq.c:1239 dev_qdisc_enqueue+0x48/0x220 net/core/dev.c:3854 __dev_xmit_skb net/core/dev.c:3943 [inline] __dev_queue_xmit+0xcd4/0x3640 net/core/dev.c:4434 packet_snd net/packet/af_packet.c:3161 [inline] packet_sendmsg+0x38d9/0x4a30 net/packet/af_packet.c:3193 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] ____sys_sendmsg+0x61b/0x980 net/socket.c:2595 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2687 [inline] __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fa3b2d9e0d9 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:00007fa3b3ca2028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fa3b3025fa0 RCX: 00007fa3b2d9e0d9 RDX: 0000000000004005 RSI: 0000200000000280 RDI: 0000000000000007 RBP: 00007fa3b2e35024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa3b3026038 R14: 00007fa3b3025fa0 R15: 00007ffdcb2163b8