syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5968/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=12681, q=836 ncpus=2)
task:syz-executor    state:R  running task     stack:18792 pid:5968  tgid:5968  ppid:5963   task_flags:0x400140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5258 [inline]
 __schedule+0x150e/0x5070 kernel/sched/core.c:6866
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7193
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:kasan_check_range+0x1dd/0x2c0 mm/kasan/generic.c:200
Code: e4 49 0f 49 dc 48 83 e3 f8 49 29 dc 74 12 41 80 3b 00 0f 85 b8 00 00 00 49 ff c3 49 ff cc 75 ee 5b 41 5c 41 5d 41 5e 41 5f 5d <c3> cc cc cc cc cc 45 84 ff 75 63 41 f7 c7 00 ff 00 00 75 5f 41 f7
RSP: 0018:ffffc9000437f7d0 EFLAGS: 00000256
RAX: ffffc9000437f901 RBX: 0000000000000010 RCX: ffffffff81747d8e
RDX: 0000000000000001 RSI: 0000000000000010 RDI: ffffc9000437f978
RBP: 0000000000000000 R08: ffffc9000437f987 R09: 1ffff9200086ff30
R10: dffffc0000000000 R11: fffff5200086ff31 R12: ffffc9000437f978
R13: 1ffff9200086ff27 R14: ffffc9000437f978 R15: ffffc9000437f970
 __asan_memset+0x22/0x50 mm/kasan/shadow.c:84
 unwind_next_frame+0xeae/0x23d0 arch/x86/kernel/unwind_orc.c:607
 __unwind_start+0x5b9/0x760 arch/x86/kernel/unwind_orc.c:773
 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:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6674 [inline]
 kmem_cache_free+0x197/0x620 mm/slub.c:6785
 user_path_at+0x44/0x60 fs/namei.c:3569
 __do_sys_pivot_root fs/namespace.c:4543 [inline]
 __se_sys_pivot_root+0x1db/0xbf0 fs/namespace.c:4526
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f503cf8f749
RSP: 002b:00007ffcb3bcd538 EFLAGS: 00000246 ORIG_RAX: 000000000000009b
RAX: ffffffffffffffda RBX: 00007f503d0143a5 RCX: 00007f503cf8f749
RDX: 00007f503cf8de97 RSI: 00007f503d0145d9 RDI: 00007f503d0143a5
RBP: 00007f503d0145d9 R08: 0000000000000000 R09: 00007ffcb3bcd5b0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f503cfef400
R13: 00007f503cfef3d8 R14: 00007ffcb3bcd838 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10438 jiffies! g12681 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:27128 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5258 [inline]
 __schedule+0x150e/0x5070 kernel/sched/core.c:6866
 __schedule_loop kernel/sched/core.c:6948 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6963
 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+0x599/0xb30 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: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: cc cc cc cc 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 33 0e 21 00 f3 0f 1e fa fb f4 <e9> 48 ee 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197de0 EFLAGS: 000002c6
RAX: 50036b2c6c775500 RBX: ffffffff8197c6ba RCX: 50036b2c6c775500
RDX: 0000000000000001 RSI: ffffffff8daa9dc3 RDI: ffffffff8be247e0
RBP: ffffc90000197f10 R08: ffff8880b87336db R09: 1ffff110170e66db
R10: dffffc0000000000 R11: ffffed10170e66dc R12: ffffffff8fc3d070
R13: 1ffff11003adeb70 R14: 0000000000000001 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888125adc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000002 CR3: 00000000355f6000 CR4: 00000000003526f0
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:191 [inline]
 do_idle+0x1ea/0x520 kernel/sched/idle.c:332
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x147
 </TASK>