syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P7524/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=17193, q=416 ncpus=2)
task:syz.4.398       state:R  running task     stack:24344 pid:7524  tgid:7520  ppid:5814   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190
 irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__rcu_read_lock+0xa7/0xf0 kernel/rcu/tree_plugin.h:416
Code: 48 b8 00 00 00 00 00 fc ff df 89 9d 84 04 00 00 65 48 8b 1d e3 b1 0f 12 48 8d bb 84 04 00 00 48 89 fa 48 c1 ea 03 0f b6 14 02 <48> 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 1f 8b 83 84 04 00
RSP: 0018:ffffc9000587e8a8 EFLAGS: 00000a07
RAX: dffffc0000000000 RBX: ffff8880753924c0 RCX: ffffc9000587e9c8
RDX: 0000000000000000 RSI: ffffffff81a9639e RDI: ffff888075392944
RBP: ffff8880753924c0 R08: 0000000000000001 R09: 000000004a498739
R10: 0000000000000002 R11: 000000000000637a R12: ffffffff81a960f0
R13: ffffc9000587e930 R14: 0000000000000000 R15: ffff8880753924c0
 rcu_read_lock include/linux/rcupdate.h:865 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xae/0x20b0 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6670 [inline]
 kmem_cache_free+0x2d8/0x770 mm/slub.c:6781
 kfree_skbmem+0x1a4/0x1f0 net/core/skbuff.c:1130
 __kfree_skb net/core/skbuff.c:1197 [inline]
 consume_skb net/core/skbuff.c:1428 [inline]
 consume_skb+0xcc/0x100 net/core/skbuff.c:1422
 netlink_broadcast_filtered+0x3ee/0xf90 net/netlink/af_netlink.c:1535
 nlmsg_multicast_filtered include/net/netlink.h:1165 [inline]
 nlmsg_multicast include/net/netlink.h:1184 [inline]
 nlmsg_notify+0x9e/0x220 net/netlink/af_netlink.c:2593
 br_vlan_notify+0x42c/0x8a0 net/bridge/br_vlan.c:1969
 __vlan_add+0x2312/0x2df0 net/bridge/br_vlan.c:299
 nbp_vlan_add+0x261/0x3f0 net/bridge/br_vlan.c:1343
 br_vlan_info+0x159/0x3d0 net/bridge/br_netlink.c:705
 br_process_vlan_info+0x435/0xa10 net/bridge/br_netlink.c:768
 br_afspec+0x573/0x650 net/bridge/br_netlink.c:836
 br_setlink+0x374/0x630 net/bridge/br_netlink.c:1135
 rtnl_bridge_setlink+0x56d/0x740 net/core/rtnetlink.c:5534
 rtnetlink_rcv_msg+0x3c9/0xe90 net/core/rtnetlink.c:6967
 netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa5d/0xc30 net/socket.c:2592
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2646
 __sys_sendmsg+0x16d/0x220 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe9b3b8f749
RSP: 002b:00007fe9b4a04038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fe9b3de6180 RCX: 00007fe9b3b8f749
RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000009
RBP: 00007fe9b3c13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe9b3de6218 R14: 00007fe9b3de6180 R15: 00007ffcf01deae8
 </TASK>
rcu: rcu_preempt kthread starved for 10557 jiffies! g17193 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:28328 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6960
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: c6 5f 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 13 49 12 00 fb f4 <e9> cc 35 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffffff8e007df8 EFLAGS: 000002c6
RAX: 0000000000cd5e23 RBX: 0000000000000000 RCX: ffffffff8b7816d9
RDX: 0000000000000000 RSI: ffffffff8dace4f3 RDI: ffffffff8bf2b480
RBP: fffffbfff1c12f68 R08: 0000000000000001 R09: ffffed101708673d
R10: ffff8880b84339eb R11: ffffffff8e098670 R12: 0000000000000000
R13: ffffffff8e097b40 R14: ffffffff9088b9d0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3bb6a4 CR3: 000000004b937000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x38d/0x510 kernel/sched/idle.c:332
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:430
 rest_init+0x16b/0x2b0 init/main.c:757
 start_kernel+0x3ef/0x4d0 init/main.c:1206
 x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x148
 </TASK>