syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P18403/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=87813, q=881926 ncpus=2)
task:syz.7.3148      state:R  running task     stack:23496 pid:18403 tgid:18402 ppid:8303   task_flags:0x400140 flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7109
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:307
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:hash_ipportip4_list+0x3cc/0x11c0 net/netfilter/ipset/ip_set_hash_gen.h:1377
Code: 00 48 8d 1c c1 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 e3 b7 5a f8 48 8b 03 48 89 44 24 68 e8 e6 1e a6 01 89 c3 <31> ff 89 c6 e8 0b aa f8 f7 85 db 74 1f e8 72 7c de f7 89 c3 31 ff
RSP: 0018:ffffc90005046960 EFLAGS: 00000246
RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffff888040b8bc00
RDX: ffffc900149f6000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc90005046b10 R08: 0000000000000000 R09: ffffffff89c7a617
R10: dffffc0000000000 R11: fffffbfff1f43b9f R12: ffff88804ecc9660
R13: dffffc0000000000 R14: ffff888077fbbe90 R15: ffff888077fbbdc0
 ip_set_dump_do+0xf45/0x1620 net/netfilter/ipset/ip_set_core.c:1660
 netlink_dump+0x6de/0xe60 net/netlink/af_netlink.c:2327
 __netlink_dump_start+0x5cb/0x7e0 net/netlink/af_netlink.c:2442
 netlink_dump_start include/linux/netlink.h:341 [inline]
 ip_set_dump+0x13e/0x1c0 net/netfilter/ipset/ip_set_core.c:1717
 nfnetlink_rcv_msg+0xb4d/0x1130 net/netfilter/nfnetlink.c:302
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
 nfnetlink_rcv+0x26a/0x2520 net/netfilter/nfnetlink.c:667
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x75c/0x8e0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:727
 ____sys_sendmsg+0x505/0x830 net/socket.c:2566
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
 __sys_sendmsg net/socket.c:2652 [inline]
 __do_sys_sendmsg net/socket.c:2657 [inline]
 __se_sys_sendmsg net/socket.c:2655 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f02e9d8e9a9
RSP: 002b:00007f02eabaf038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f02e9fb5fa0 RCX: 00007f02e9d8e9a9
RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000000000000004
RBP: 00007f02e9e10d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f02e9fb5fa0 R15: 00007ffd202f1b98
 </TASK>
rcu: rcu_preempt kthread starved for 414 jiffies! g87813 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:26888 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6879
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2054
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2256
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </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: 3396 Comm: kworker/R-krdsd Not tainted 6.16.0-rc7-syzkaller-00018-g01a412d06bc5 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: krdsd rds_connect_worker
RIP: 0010:ipv4_conntrack_local+0x5/0x210 net/netfilter/nf_conntrack_proto.c:213
Code: 89 f6 e8 8e 5e 20 f8 4c 89 f7 48 89 de 5b 41 5e e9 b0 a6 fe ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <41> 57 41 56 41 55 41 54 53 49 89 d6 48 89 f3 49 bc 00 00 00 00 00
RSP: 0018:ffffc90000006f80 EFLAGS: 00000246
RAX: 1ffff1100f9c4606 RBX: ffffffff899fc860 RCX: ffff888030bd3c00
RDX: ffffc90000007040 RSI: ffff888063859780 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff888030bd3c00 R09: 0000000000000004
R10: 0000000000000003 R11: ffffffff899fc860 R12: 0000000000000002
R13: ffff88807ce23028 R14: 1ffff1100f9c4600 R15: ffff88807ce23030
FS:  0000000000000000(0000) GS:ffff888125c23000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f64b8c00218 CR3: 0000000076428000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 nf_hook_entry_hookfn include/linux/netfilter.h:157 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
 nf_hook+0x217/0x380 include/linux/netfilter.h:272
 __ip_local_out+0x4db/0x600 net/ipv4/ip_output.c:118
 ip_local_out+0x26/0x70 net/ipv4/ip_output.c:127
 synproxy_send_client_synack+0x8bb/0xe20 net/netfilter/nf_synproxy_core.c:484
 nft_synproxy_eval_v4+0x36e/0x560 net/netfilter/nft_synproxy.c:59
 nft_synproxy_do_eval+0x345/0x570 net/netfilter/nft_synproxy.c:141
 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline]
 nft_do_chain+0x40c/0x1920 net/netfilter/nf_tables_core.c:285
 nft_do_chain_inet+0x25d/0x340 net/netfilter/nft_chain_filter.c:161
 nf_hook_entry_hookfn include/linux/netfilter.h:157 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:272 [inline]
 NF_HOOK+0x206/0x3a0 include/linux/netfilter.h:315
 NF_HOOK+0x30c/0x3a0 include/linux/netfilter.h:317
 __netif_receive_skb_one_core net/core/dev.c:5977 [inline]
 __netif_receive_skb+0x143/0x380 net/core/dev.c:6090
 process_backlog+0x60e/0x14f0 net/core/dev.c:6442
 __napi_poll+0xc7/0x480 net/core/dev.c:7414
 napi_poll net/core/dev.c:7478 [inline]
 net_rx_action+0x707/0xe30 net/core/dev.c:7605
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 do_softirq+0xec/0x180 kernel/softirq.c:480
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x17d/0x1c0 kernel/softirq.c:407
 rds_tcp_tune+0xc8/0x4f0 net/rds/tcp.c:497
 rds_tcp_conn_path_connect+0x2a1/0x680 net/rds/tcp_connect.c:127
 rds_connect_worker+0x1d8/0x290 net/rds/threads.c:176
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
 rescuer_thread+0x53c/0xdd0 kernel/workqueue.c:3498
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>