============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.2.45252/7082 is trying to acquire lock: ffff8880743c1098 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] ffff8880743c1098 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] ffff8880743c1098 (_xmit_ETHER#2){+.-.}-{2:2}, at: __dev_queue_xmit+0x14b5/0x2fd0 net/core/dev.c:4297 but task is already holding lock: ffff88807cd8b498 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] ffff88807cd8b498 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] ffff88807cd8b498 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x162/0x4b0 net/sched/sch_generic.c:343 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(_xmit_ETHER#2); lock(_xmit_ETHER#2); *** DEADLOCK *** May be due to missing lock nesting notation 10 locks held by syz.2.45252/7082: #0: ffff888026d40960 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1744 [inline] #0: ffff888026d40960 (sk_lock-AF_INET){+.+.}-{0:0}, at: sctp_sendmsg+0xa70/0x2900 net/sctp/socket.c:1969 #1: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #2: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #3: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #4: ffff88802c95d258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] #4: ffff88802c95d258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #4: ffff88802c95d258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] #4: ffff88802c95d258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x1120/0x2fd0 net/core/dev.c:4266 #5: ffff88807cd8b498 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #5: ffff88807cd8b498 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] #5: ffff88807cd8b498 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x162/0x4b0 net/sched/sch_generic.c:343 #6: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #7: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #8: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 #9: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 stack backtrace: CPU: 0 PID: 7082 Comm: syz.2.45252 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 __lock_acquire+0x1236/0x7d10 kernel/locking/lockdep.c:-1 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:364 [inline] __netif_tx_lock include/linux/netdevice.h:4446 [inline] __dev_queue_xmit+0x14b5/0x2fd0 net/core/dev.c:4297 br_dev_queue_push_xmit+0x692/0x850 net/bridge/br_forward.c:53 NF_HOOK+0x2f9/0x380 include/linux/netfilter.h:302 br_forward_finish+0x74/0x80 net/bridge/br_forward.c:66 NF_HOOK+0x2f9/0x380 include/linux/netfilter.h:302 __br_forward+0x433/0x610 net/bridge/br_forward.c:115 deliver_clone net/bridge/br_forward.c:131 [inline] maybe_deliver+0xb5/0x150 net/bridge/br_forward.c:190 br_flood+0x2fc/0x450 net/bridge/br_forward.c:232 br_dev_xmit+0x922/0x14b0 net/bridge/br_device.c:88 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3678 __dev_queue_xmit+0x1a78/0x2fd0 net/core/dev.c:4301 neigh_output include/net/neighbour.h:509 [inline] ip_finish_output2+0xcbf/0x10a0 net/ipv4/ip_output.c:228 iptunnel_xmit+0x4d6/0x8e0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1905/0x2280 net/ipv4/ip_tunnel.c:824 __gre_xmit net/ipv4/ip_gre.c:474 [inline] erspan_xmit+0x9d5/0x15a0 net/ipv4/ip_gre.c:723 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3678 sch_direct_xmit+0x25a/0x4b0 net/sched/sch_generic.c:345 __dev_xmit_skb net/core/dev.c:3897 [inline] __dev_queue_xmit+0x179f/0x2fd0 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 dst_output include/net/dst.h:452 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] __ip_queue_xmit+0x11c1/0x1c00 net/ipv4/ip_output.c:538 sctp_packet_transmit+0x239c/0x2910 net/sctp/output.c:652 sctp_packet_singleton+0x231/0x330 net/sctp/outqueue.c:780 sctp_outq_flush_ctrl net/sctp/outqueue.c:911 [inline] sctp_outq_flush+0x4ac/0x3100 net/sctp/outqueue.c:1209 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline] sctp_do_sm+0x4ee2/0x55f0 net/sctp/sm_sideeffect.c:1170 sctp_primitive_ASSOCIATE+0x91/0xc0 net/sctp/primitive.c:73 sctp_sendmsg_to_asoc+0x14a7/0x1d90 net/sctp/socket.c:1840 sctp_sendmsg+0x196a/0x2900 net/sctp/socket.c:2030 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: 0033:0x7f00c64e3f79 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:00007f00c473e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f00c675dfa0 RCX: 00007f00c64e3f79 RDX: 00000000000003e8 RSI: 00002000000004c0 RDI: 0000000000000006 RBP: 00007f00c657a7e0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f00c675e038 R14: 00007f00c675dfa0 R15: 00007ffe2ca56e58 syz.2.45252 (7082) used greatest stack depth: 16432 bytes left