syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P9498/1:b..l
	(detected by 0, t=10502 jiffies, g=51197, q=16)
task:syz.2.1142      state:R  running task     stack:25056 pid: 9498 ppid:  4203 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0000:ffffc90002fdf320 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 1826c56c74da2a00
RDX: 0000000000000000 RSI: ffffffff8a0b2e80 RDI: ffffffff8a59e800
RBP: ffffc90002fdf430 R08: dffffc0000000000 R09: fffffbfff1ff5419
R10: fffffbfff1ff5419 R11: 1ffffffff1ff5418 R12: ffffffff8c11c720
R13: 1ffff920005fbe70 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire+0x20/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 percpu_ref_put_many include/linux/percpu-refcount.h:317 [inline]
 percpu_ref_put+0x16/0x150 include/linux/percpu-refcount.h:338
 css_put include/linux/cgroup.h:405 [inline]
 __mem_cgroup_charge+0x52/0x80 mm/memcontrol.c:6802
 mem_cgroup_charge include/linux/memcontrol.h:700 [inline]
 shmem_add_to_page_cache+0xa83/0x14b0 mm/shmem.c:718
 shmem_getpage_gfp+0x1793/0x2d40 mm/shmem.c:1940
 shmem_fault+0x1a9/0x520 mm/shmem.c:2118
 __do_fault+0x141/0x330 mm/memory.c:3928
 do_read_fault mm/memory.c:4264 [inline]
 do_fault mm/memory.c:4392 [inline]
 handle_pte_fault mm/memory.c:4650 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x2946/0x43b0 mm/memory.c:4883
 faultin_page mm/gup.c:976 [inline]
 __get_user_pages+0x93e/0x11c0 mm/gup.c:1197
 populate_vma_page_range+0x213/0x290 mm/gup.c:1529
 __mm_populate+0x26f/0x3a0 mm/gup.c:1638
 mm_populate include/linux/mm.h:2646 [inline]
 vm_mmap_pgoff+0x203/0x2b0 mm/util.c:556
 ksys_mmap_pgoff+0x140/0x780 mm/mmap.c:1635
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fb960658749
RSP: 002b:00007fb95e8bf038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fb9608aefa0 RCX: 00007fb960658749
RDX: 0000000000000003 RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007fb9606dcf91 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb9608af038 R14: 00007fb9608aefa0 R15: 00007ffda51715c8
 </TASK>
rcu: rcu_preempt kthread starved for 10543 jiffies! g51197 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:28064 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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 PID: 9502 Comm: syz.1.1140 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__dequeue_signal+0x4c4/0x5d0 kernel/signal.c:620
Code: f7 e8 c0 fc 71 00 49 c7 06 00 00 00 00 eb 0c e8 92 93 2d 00 eb 14 e8 8b 93 2d 00 48 8b 3d 54 1d a2 0d 4c 89 ee e8 4c 32 71 00 <89> d8 48 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 66 93 2d 00
RSP: 0018:ffffc900030afb20 EFLAGS: 00000093
RAX: ffffffff814a348d RBX: 0000000000000000 RCX: ffff888074b7bb80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff888074b7c4d8 R08: 0000000000000004 R09: 0000000000000003
R10: fffff52000615f58 R11: 1ffff92000615f58 R12: 0000000000000000
R13: 1ffff1100e96f89b R14: 0000000000000000 R15: ffff888074b7c4c8
FS:  000055558d39d500(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c254118 CR3: 000000005a578000 CR4: 00000000003526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dequeue_signal+0x46/0x440 kernel/signal.c:637
 get_signal+0x6fe/0x12c0 kernel/signal.c:2781
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f629f78c134
Code: 00 48 85 db 74 0a 48 89 5c 24 10 e9 62 fe ff ff 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 0f 1f 80 00 00 00 00 53 48 89 fb <48> 85 ff 74 47 80 3d a4 f5 eb 00 00 75 1e 80 3d 6f bf 38 00 00 75
RSP: 002b:00007ffc0f41b110 EFLAGS: 00000202
RAX: 00000000000000f0 RBX: 00007f629fb1c128 RCX: 0000000000000000
RDX: 00007f629fb1c090 RSI: 00007f629fb1bfa0 RDI: 00007f629fb1c128
RBP: 0000000000000001 R08: 00007f629fb1bfa0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00007f629fb1c09c
R13: 00007f629fb1c090 R14: 000000000000126b R15: 0000000000000004
 </TASK>