syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10076/1:b..l
rcu: 	(detected by 0, t=10506 jiffies, g=37509, q=136 ncpus=2)
task:syz.2.1125      state:R  running task     stack:29064 pid:10076 tgid:10074 ppid:5807   task_flags:0x400040 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_is_watching+0x80/0xc0 kernel/rcu/tree.c:752
Code: 89 da 48 c1 ea 03 0f b6 14 02 48 89 d8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 24 8b 03 c1 e8 02 83 e0 01 65 ff 0d 50 9e 0f 12 <74> 07 5b 5d c3 cc cc cc cc e8 02 f5 88 ff 5b 5d c3 cc cc cc cc 48
RSP: 0018:ffffc9001d05f7c8 EFLAGS: 00000286
RAX: 0000000000000001 RBX: ffff8880b85339e8 RCX: ffffc9001d060001
RDX: 0000000000000000 RSI: ffffffff8bf2b380 RDI: ffffffff8dd7bf28
RBP: 0000000000000001 R08: 0000000000000001 R09: 00000000fd7aaf96
R10: 0000000000000002 R11: 00000000000356ae R12: ffffffff816cb9a4
R13: ffffc9001d05f898 R14: ffffc9001d05ff18 R15: ffffc9001d05f8cc
 trace_lock_release include/trace/events/lock.h:69 [inline]
 lock_release+0x201/0x2d0 kernel/locking/lockdep.c:5879
 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+0x3f9/0x20b0 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:56
 kasan_save_track+0x14/0x30 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __do_kmalloc_node mm/slub.c:5657 [inline]
 __kmalloc_noprof+0x33d/0x910 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 lsm_blob_alloc+0x68/0x90 security/security.c:192
 lsm_ipc_alloc security/security.c:257 [inline]
 security_sem_alloc+0x24/0x230 security/security.c:3518
 newary+0x226/0xc50 ipc/sem.c:553
 ipcget_new ipc/util.c:345 [inline]
 ipcget+0xf6/0xfa0 ipc/util.c:674
 ksys_semget ipc/sem.c:621 [inline]
 __do_sys_semget ipc/sem.c:626 [inline]
 __se_sys_semget ipc/sem.c:624 [inline]
 __x64_sys_semget+0x1cb/0x260 ipc/sem.c:624
 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: 0033:0x7fa598f8f749
RSP: 002b:00007fa599e55038 EFLAGS: 00000246 ORIG_RAX: 0000000000000040
RAX: ffffffffffffffda RBX: 00007fa5991e6090 RCX: 00007fa598f8f749
RDX: 0000000000000000 RSI: 0000004000000009 RDI: 0000000000000000
RBP: 00007fa599013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa5991e6128 R14: 00007fa5991e6090 R15: 00007ffd2235c008
 </TASK>
rcu: rcu_preempt kthread starved for 10501 jiffies! g37509 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:27928 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:
CPU: 0 UID: 0 PID: 10075 Comm: syz.2.1125 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:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0xe02/0x15e0 kernel/smp.c:877
Code: 10 4c 89 74 24 10 49 89 d5 48 89 d5 48 89 54 24 18 49 c1 ed 03 83 e5 07 4d 01 e5 83 c5 03 e8 35 5b 0c 00 f3 90 41 0f b6 45 00 <40> 38 c5 7c 08 84 c0 0f 85 b6 05 00 00 8b 43 08 31 ff 83 e0 01 41
RSP: 0018:ffffc9001ce87598 EFLAGS: 00000293
RAX: 0000000000000000 RBX: ffff8880b8540cc0 RCX: ffffffff81b28b61
RDX: ffff8880275224c0 RSI: ffffffff81b28b3b RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: ffff888027522ff0 R12: dffffc0000000000
R13: ffffed10170a8199 R14: 0000000000000001 R15: 0000000000000001
FS:  00007fa599e766c0(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000a038 CR3: 00000000558f9000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1043
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1382 [inline]
 flush_tlb_mm_range+0x2f0/0x12c0 arch/x86/mm/tlb.c:1472
 flush_tlb_page arch/x86/include/asm/tlbflush.h:324 [inline]
 ptep_clear_flush+0x136/0x180 mm/pgtable-generic.c:103
 wp_page_copy mm/memory.c:3785 [inline]
 do_wp_page+0x171f/0x5010 mm/memory.c:4180
 handle_pte_fault mm/memory.c:6289 [inline]
 __handle_mm_fault+0x1bd2/0x2bb0 mm/memory.c:6411
 handle_mm_fault+0x3fe/0xad0 mm/memory.c:6580
 do_user_addr_fault+0x7a6/0x1370 arch/x86/mm/fault.c:1387
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x64/0xc0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0010:__put_user_4+0xd/0x20 arch/x86/lib/putuser.S:94
Code: 66 89 01 31 c9 0f 01 ca c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 48 89 cb 48 c1 fb 3f 48 09 d9 0f 01 cb <89> 01 31 c9 0f 01 ca e9 c7 c0 03 00 0f 1f 80 00 00 00 00 90 90 90
RSP: 0018:ffffc9001ce87ce0 EFLAGS: 00050202
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000020000000a038
RDX: ffff8880275224c0 RSI: ffffffff893c1699 RDI: ffffffff8bf2b400
RBP: 0000000000000072 R08: 00000000ffffffff R09: 00000000ffffffff
R10: 0000000000000001 R11: ffff888027522ff0 R12: 0000000004048890
R13: 000020000000a000 R14: 0000000000000173 R15: 0000000000000174
 __sys_sendmmsg+0x234/0x420 net/socket.c:2740
 __do_sys_sendmmsg net/socket.c:2762 [inline]
 __se_sys_sendmmsg net/socket.c:2759 [inline]
 __x64_sys_sendmmsg+0x9c/0x100 net/socket.c:2759
 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: 0033:0x7fa598f8f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa599e76038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fa5991e5fa0 RCX: 00007fa598f8f749
RDX: 0400000000000174 RSI: 0000200000008380 RDI: 0000000000000003
RBP: 00007fa599013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000004008890 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa5991e6038 R14: 00007fa5991e5fa0 R15: 00007ffd2235c008
 </TASK>