syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P36/1:b..l P5863/1:b..l P6403/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=12765, q=1147 ncpus=2)
task:syz.1.105       state:R  running task     stack:24392 pid:6403  tgid:6402  ppid:5842   task_flags:0x400040 flags:0x00080001
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7256
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:native_irq_disable arch/x86/include/asm/irqflags.h:37 [inline]
RIP: 0010:arch_local_irq_disable arch/x86/include/asm/irqflags.h:114 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:128 [inline]
RIP: 0010:lock_release+0xaf/0x3e0 kernel/locking/lockdep.c:5885
Code: 0b 00 00 00 0f 85 1e 02 00 00 49 81 3e 40 33 0e 93 0f 84 11 02 00 00 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 48 8b 5c 24 20 <fa> 48 c7 c7 6f 87 52 8d e8 54 37 9c 09 65 ff 05 ad af ae 10 c7 44
RSP: 0018:ffffc9000bed6e70 EFLAGS: 00000206
RAX: 0000000000000000 RBX: 0000000000000206 RCX: b821ac2effc3f700
RDX: ffffc9000bed6f01 RSI: ffffffff8b9ee940 RDI: ffffffff8b9ee900
RBP: dffffc0000000000 R08: ffffc9000bed70d0 R09: ffffc9000bed6ff8
R10: dffffc0000000000 R11: fffff520017dae01 R12: ffffc9000bed70e0
R13: ffffffff81723db5 R14: ffffffff8dd3b220 R15: ffff88802cf90000
 rcu_lock_release include/linux/rcupdate.h:341 [inline]
 rcu_read_unlock include/linux/rcupdate.h:897 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0x19a9/0x2390 arch/x86/kernel/unwind_orc.c:680
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 unpoison_slab_object mm/kasan/common.c:342 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:368
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4946 [inline]
 slab_alloc_node mm/slub.c:5245 [inline]
 kmem_cache_alloc_noprof+0x367/0x6e0 mm/slub.c:5252
 dst_alloc+0x105/0x170 net/core/dst.c:89
 rt_dst_clone+0x52/0x680 net/ipv4/route.c:1674
 ip_mc_finish_output+0xe9/0x2d0 net/ipv4/ip_output.c:357
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip_mc_output+0x25c/0x590 net/ipv4/ip_output.c:401
 ip_local_out net/ipv4/ip_output.c:131 [inline]
 ip_send_skb+0x74/0x100 net/ipv4/ip_output.c:1508
 udp_send_skb+0xaf1/0x14c0 net/ipv4/udp.c:1195
 udp_sendmsg+0x195a/0x2170 net/ipv4/udp.c:1484
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x19c/0x270 net/socket.c:742
 ____sys_sendmsg+0x52d/0x830 net/socket.c:2630
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2684
 __sys_sendmmsg+0x227/0x430 net/socket.c:2773
 __do_sys_sendmmsg net/socket.c:2800 [inline]
 __se_sys_sendmmsg net/socket.c:2797 [inline]
 __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2797
 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: 0033:0x7f75dd58eec9
RSP: 002b:00007f75de468038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f75dd7e5fa0 RCX: 00007f75dd58eec9
RDX: 000000000800001d RSI: 0000200000007fc0 RDI: 0000000000000003
RBP: 00007f75dd611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f75dd7e6038 R14: 00007f75dd7e5fa0 R15: 00007ffd0a14a508
 </TASK>
task:udevd           state:R  running task     stack:24648 pid:5863  tgid:5863  ppid:5206   task_flags:0x400140 flags:0x00080001
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
 preempt_schedule_notrace+0xd1/0x110 kernel/sched/core.c:7206
 preempt_schedule_notrace_thunk+0x16/0x30 arch/x86/entry/thunk.S:13
 rcu_is_watching+0x7f/0xb0 kernel/rcu/tree.c:752
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0x5f/0x360 kernel/locking/lockdep.c:5831
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xc2/0x2390 arch/x86/kernel/unwind_orc.c:479
 __unwind_start+0x5b9/0x760 arch/x86/kernel/unwind_orc.c:758
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xe4/0x150 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 unpoison_slab_object mm/kasan/common.c:342 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:368
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4946 [inline]
 slab_alloc_node mm/slub.c:5245 [inline]
 kmem_cache_alloc_noprof+0x367/0x6e0 mm/slub.c:5252
 alloc_empty_file+0x55/0x1d0 fs/file_table.c:237
 path_openat+0x107/0x3830 fs/namei.c:4120
 do_filp_open+0x1fa/0x410 fs/namei.c:4161
 do_sys_openat2+0x121/0x1c0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1463
 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: 0033:0x7f9a6f2a7407
RSP: 002b:00007ffdd2ad2540 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f9a6fa1d880 RCX: 00007f9a6f2a7407
RDX: 0000000000080000 RSI: 000055b7d352b900 RDI: ffffffffffffff9c
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000055b7be6e195f
R13: 000055b7be6f2660 R14: 0000000000000000 R15: 00000000ffffffff
 </TASK>
task:kworker/u8:2    state:R  running task     stack:21192 pid:36    tgid:36    ppid:2      task_flags:0x4208160 flags:0x00080000
Workqueue: iou_exit io_ring_exit_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
 preempt_schedule_notrace+0xd1/0x110 kernel/sched/core.c:7206
 preempt_schedule_notrace_thunk+0x16/0x30 arch/x86/entry/thunk.S:13
 rcu_is_watching+0x7f/0xb0 kernel/rcu/tree.c:752
 rcu_read_unlock include/linux/rcupdate.h:895 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0x1965/0x2390 arch/x86/kernel/unwind_orc.c:680
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:559
 slab_free_hook mm/slub.c:2475 [inline]
 slab_free mm/slub.c:6566 [inline]
 kmem_cache_free+0x4a2/0x690 mm/slub.c:6676
 __io_req_caches_free+0x1c1/0x270 io_uring/io_uring.c:2824
 io_req_caches_free+0x21/0x60 io_uring/io_uring.c:2836
 io_ring_exit_work+0x415/0x930 io_uring/io_uring.c:3034
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x439/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread starved for 10263 jiffies! g12765 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:27320 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7026
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x439/0x7d0 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: 9e 17 d8 f5 cc cc cc 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 93 fc 0f 00 f3 0f 1e fa fb f4 <e9> 73 17 d8 f5 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffffff8da07d80 EFLAGS: 000002c2
RAX: cb834f824a19ef00 RBX: ffffffff81952927 RCX: cb834f824a19ef00
RDX: 0000000000000001 RSI: ffffffff8d51553d RDI: ffffffff8b9ee960
RBP: ffffffff8da07eb8 R08: ffff8880b8832fdb R09: 1ffff110171065fb
R10: dffffc0000000000 R11: ffffed10171065fc R12: ffffffff8f5c2230
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1b52a40
FS:  0000000000000000(0000) GS:ffff888126378000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000027f030 CR3: 0000000031175000 CR4: 0000000000350ef0
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+0x73/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:190 [inline]
 do_idle+0x1e7/0x510 kernel/sched/idle.c:330
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:428
 rest_init+0x2de/0x300 init/main.c:757
 start_kernel+0x3ae/0x410 init/main.c:1111
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x147
 </TASK>