[syzbot] [lvs?] INFO: rcu detected stall in ip_vs_estimation_kthread (2)

[syzbot] [lvs?] INFO: rcu detected stall in ip_vs_estimation_kthread (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7b63ef2d55f2 Merge tag 'for-7.3-rc6-tag' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16feaa8e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=23e5acac5c98285f
dashboard link: https://syzkaller.appspot.com/bug?extid=022ec9322756662013b5
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6a3c98d82e9c/disk-7b63ef2d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3d921ef6c68c/vmlinux-7b63ef2d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9d4e9981e5b9/bzImage-7b63ef2d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+022ec9322756662013b5@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5285/3:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=348101, q=1610 ncpus=2)
task:syz-executor    state:R  running task     stack:28200 pid:5285  tgid:5285  ppid:32677  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5533 [inline]
 __schedule+0x17db/0x58f0 kernel/sched/core.c:7284
 preempt_schedule_common+0x7f/0xd0 kernel/sched/core.c:7463
 preempt_schedule_thunk+0x16/0x40 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:201 [inline]
 _raw_spin_unlock+0x41/0x50 kernel/locking/spinlock.c:213
 spin_unlock include/linux/spinlock.h:401 [inline]
 filemap_map_pages+0x1aba/0x2170 mm/filemap.c:3997
 do_fault_around mm/memory.c:5958 [inline]
 do_read_fault mm/memory.c:5991 [inline]
 do_fault mm/memory.c:6134 [inline]
 do_pte_missing+0x20ae/0x34b0 mm/memory.c:4700
 handle_pte_fault mm/memory.c:6558 [inline]
 __handle_mm_fault mm/memory.c:6707 [inline]
 handle_mm_fault+0x1a53/0x3750 mm/memory.c:6876
 do_user_addr_fault+0xa4f/0x1340 arch/x86/mm/fault.c:1343
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x7f5254b3f7c0
RSP: 002b:00007f5254f4fc58 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 00007f5254f4fc60 RCX: 00007f5254bc6c4c
RDX: 0000000000000000 RSI: 0000000000000018 RDI: 00007f5254f4fc60
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 000055557d62f7d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 00000000001e199a R15: 00007f5254f4fe40
 </TASK>
rcu: rcu_preempt kthread starved for 737 jiffies! g348101 f0x0 RCU_GP_WAIT_FQS(5) ->state=R ->cpu=1
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:27496 pid:17    tgid:17    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5533 [inline]
 __schedule+0x17db/0x58f0 kernel/sched/core.c:7284
 __schedule_loop kernel/sched/core.c:7361 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7376
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2122
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2330
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 2226 Comm: ipvs-e:321:0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:netif_skb_features+0xc5/0xf20 net/core/dev.c:3914
Code: 4c 89 74 24 10 49 8b 45 00 48 89 44 24 18 48 8d 98 b8 00 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <74> 08 48 89 df e8 b1 57 85 f8 4c 8b 33 48 8b 44 24 10 48 8d b8 d0
RSP: 0018:ffffc90000a17da0 EFLAGS: 00000246
RAX: 1ffff1100547bc17 RBX: ffff88802a3de0b8 RCX: dffffc0000000000
RDX: 8000000000000300 RSI: 0000000000000100 RDI: ffff8881d9ce2dc0
RBP: ffffc90000a17ea0 R08: 0000000000000100 R09: 1ffffffff20f4ccf
R10: dffffc0000000000 R11: fffffbfff20f4cd0 R12: dffffc0000000000
R13: ffff8881d9ce2dd0 R14: ffff8881d9ce2dc0 R15: ffff88802a3de000
FS:  0000000000000000(0000) GS:ffff888124dc6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5254b3f7c0 CR3: 000000007eb18000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 validate_xmit_skb+0xa0/0x1820 net/core/dev.c:4095
 __dev_queue_xmit+0xb01/0x3920 net/core/dev.c:4945
 dev_queue_xmit include/linux/netdevice.h:3464 [inline]
 neigh_hh_output include/net/neighbour.h:544 [inline]
 neigh_output include/net/neighbour.h:558 [inline]
 ip_finish_output2+0xbda/0x10b0 net/ipv4/ip_output.c:236
 NF_HOOK_COND include/linux/netfilter.h:314 [inline]
 ip_output+0x29f/0x450 net/ipv4/ip_output.c:437
 synproxy_send_client_synack+0x89b/0xde0 net/netfilter/nf_synproxy_core.c:487
 nft_synproxy_eval_v4+0x362/0x4e0 net/netfilter/nft_synproxy.c:59
 nft_synproxy_do_eval+0x389/0x5d0 net/netfilter/nft_synproxy.c:142
 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline]
 nft_do_chain+0x48d/0x1b10 net/netfilter/nf_tables_core.c:285
 nft_do_chain_ipv4+0x195/0x290 net/netfilter/nft_chain_filter.c:24
 nf_hook_entry_hookfn include/linux/netfilter.h:165 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:280 [inline]
 NF_HOOK+0x21f/0x3c0 include/linux/netfilter.h:323
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:325
 __netif_receive_skb_one_core net/core/dev.c:6297 [inline]
 __netif_receive_skb net/core/dev.c:6410 [inline]
 process_backlog+0xa6b/0x18b0 net/core/dev.c:6761
 __napi_poll+0xaa/0x330 net/core/dev.c:7830
 napi_poll net/core/dev.c:7893 [inline]
 net_rx_action+0x61d/0xf50 net/core/dev.c:8050
 handle_softirqs+0x226/0x860 kernel/softirq.c:645
 __do_softirq kernel/softirq.c:679 [inline]
 invoke_softirq kernel/softirq.c:519 [inline]
 __irq_exit_rcu+0xcb/0x220 kernel/softirq.c:758
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:775
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:finish_task_switch+0x413/0xc60 kernel/sched/core.c:5384
Code: 04 00 00 41 c7 84 24 20 0e 00 00 00 00 00 00 e9 db 06 00 00 49 83 c4 48 4c 89 e7 e8 47 e0 53 0a e8 22 2f 3a 00 fb 4c 8b 65 c8 <49> 8d bc 24 18 17 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0
RSP: 0018:ffffc90003c477e0 EFLAGS: 00000206
RAX: 000000000001ad27 RBX: ffff8880b873c8e0 RCX: 8000000000000001
RDX: 0000000000000000 RSI: ffffffff8e41727c RDI: ffffffff8c6dad80
RBP: ffffc90003c47830 R08: ffffffff907a667f R09: 1ffffffff20f4ccf
R10: dffffc0000000000 R11: fffffbfff20f4cd0 R12: ffff888033593e80
R13: ffff8880b873c8a8 R14: dffffc0000000000 R15: 1ffff110170e791c
 context_switch kernel/sched/core.c:5536 [inline]
 __schedule+0x17e3/0x58f0 kernel/sched/core.c:7284
 __schedule_loop kernel/sched/core.c:7361 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7376
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 ip_vs_estimation_kthread+0x29ef/0x3950 net/netfilter/ipvs/ip_vs_est.c:216
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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