syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10011/2:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=31869, q=1105 ncpus=2)
task:syz.3.807       state:R  running task     stack:25016 pid:10011 tgid:10009 ppid:5817   task_flags:0x2040044c flags:0x00080001
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:__sanitizer_cov_trace_cmp4+0x8/0x20 kernel/kcov.c:288
Code: bf 02 00 00 00 e9 18 ff ff ff 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 8b 0c 24 <89> f2 89 fe bf 04 00 00 00 e9 ea fe ff ff 66 2e 0f 1f 84 00 00 00
RSP: 0018:ffffc900037f6c38 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 000000000000022e RCX: ffffffff81cebac3
RDX: ffff88802c678000 RSI: 000000000000022e RDI: 000000000000022e
RBP: 0000000000000000 R08: 0000000000000006 R09: 00007f59e2b8f749
R10: ffffffffa0201660 R11: ffff88802c678b30 R12: 00007f59e2b8f749
R13: dffffc0000000000 R14: 000000000000022e R15: ffffffffa0201660
 latch_tree_find include/linux/rbtree_latch.h:211 [inline]
 bpf_ksym_find+0x103/0x1c0 kernel/bpf/core.c:712
 is_bpf_text_address+0x58/0x1a0 kernel/bpf/core.c:745
 kernel_text_address kernel/extable.c:125 [inline]
 kernel_text_address+0x8d/0x100 kernel/extable.c:94
 __kernel_text_address+0xd/0x40 kernel/extable.c:79
 unwind_get_return_address+0x59/0xa0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0xa6/0x100 arch/x86/kernel/stacktrace.c:26
 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
 kmalloc_noprof include/linux/slab.h:957 [inline]
 slab_free_hook mm/slub.c:2492 [inline]
 slab_free mm/slub.c:6663 [inline]
 kmem_cache_free+0x147/0x770 mm/slub.c:6774
 mempool_free+0xde/0x130 mm/mempool.c:712
 bio_put_percpu_cache block/bio.c:806 [inline]
 bio_put+0x355/0x5b0 block/bio.c:825
 bio_endio+0x751/0x8a0 block/bio.c:1673
 blk_update_request+0x914/0x15c0 block/blk-mq.c:1006
 blk_mq_end_request+0x59/0x430 block/blk-mq.c:1168
 blk_mq_complete_request block/blk-mq.c:1346 [inline]
 blk_mq_complete_request+0x8b/0xb0 block/blk-mq.c:1343
 nullb_complete_cmd drivers/block/null_blk/main.c:1402 [inline]
 null_handle_cmd drivers/block/null_blk/main.c:1454 [inline]
 null_queue_rq+0xb69/0xfd0 drivers/block/null_blk/main.c:1693
 null_queue_rqs+0xe9/0x2f0 drivers/block/null_blk/main.c:1707
 __blk_mq_flush_list block/blk-mq.c:2847 [inline]
 __blk_mq_flush_list+0x9a/0xc0 block/blk-mq.c:2843
 blk_mq_dispatch_queue_requests+0x184/0x7b0 block/blk-mq.c:2892
 blk_mq_flush_plug_list+0x1f2/0x600 block/blk-mq.c:2980
 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1225
 blk_finish_plug block/blk-core.c:1252 [inline]
 blk_finish_plug+0x53/0xa0 block/blk-core.c:1249
 blkdev_writepages+0xe9/0x140 block/fops.c:492
 do_writepages+0x27a/0x600 mm/page-writeback.c:2598
 filemap_writeback+0x225/0x2d0 mm/filemap.c:387
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 filemap_write_and_wait_range mm/filemap.c:684 [inline]
 filemap_write_and_wait_range+0xa6/0x130 mm/filemap.c:675
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev block/bdev.c:277 [inline]
 sync_blockdev block/bdev.c:273 [inline]
 bdev_release+0x4d3/0x6d0 block/bdev.c:1143
 blkdev_release+0x15/0x20 block/fops.c:710
 __fput+0x402/0xb70 fs/file_table.c:468
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x87f/0x2bd0 kernel/exit.c:971
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1112
 get_signal+0x2671/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x8c/0x540 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x4ee/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f59e2b8f749
RSP: 002b:00007f59e39830e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f59e2de6098 RCX: 00007f59e2b8f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f59e2de6098
RBP: 00007f59e2de6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f59e2de6128 R14: 00007fff47d93500 R15: 00007fff47d935e8
 </TASK>
rcu: rcu_preempt kthread starved for 10373 jiffies! g31869 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:28488 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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 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:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: 06 60 02 c3 cc cc cc cc 0f 1f 00 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 13 59 13 00 fb f4 <e9> cc 35 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffffff8e007df8 EFLAGS: 000002c6
RAX: 00000000020bf497 RBX: 0000000000000000 RCX: ffffffff8b7706d9
RDX: 0000000000000000 RSI: ffffffff8dac200a RDI: ffffffff8bf24280
RBP: fffffbfff1c12f68 R08: 0000000000000001 R09: ffffed101708673d
R10: ffff8880b84339eb R11: ffffffff8e098670 R12: 0000000000000000
R13: ffffffff8e097b40 R14: ffffffff9087f7d0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124909000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fd22ff8 CR3: 000000000e184000 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+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x38d/0x510 kernel/sched/idle.c:332
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:430
 rest_init+0x16b/0x2b0 init/main.c:757
 start_kernel+0x3ef/0x4d0 init/main.c:1206
 x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x148
 </TASK>