syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5785/1:b..l P2945/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=12353, q=231 ncpus=2)
task:kworker/u4:8    state:R  running task     stack:20952 pid:2945  ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 preempt_schedule_notrace+0xce/0x110 kernel/sched/core.c:6960
 preempt_schedule_notrace_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:46
 rcu_is_watching+0x7a/0xb0 kernel/rcu/tree.c:701
 rcu_read_lock include/linux/rcupdate.h:787 [inline]
 unlocked_inode_to_wb_begin include/linux/backing-dev.h:290 [inline]
 folio_clear_dirty_for_io+0x27b/0xc30 mm/page-writeback.c:2928
 mpage_submit_folio+0x7d/0x3c0 fs/ext4/inode.c:1884
 mpage_map_and_submit_buffers fs/ext4/inode.c:2149 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2288 [inline]
 ext4_do_writepages+0x1d01/0x38d0 fs/ext4/inode.c:2713
 ext4_writepages+0x1a8/0x2f0 fs/ext4/inode.c:2802
 do_writepages+0x3a2/0x600 mm/page-writeback.c:2575
 __writeback_single_inode+0x153/0xee0 fs/fs-writeback.c:1625
 writeback_sb_inodes+0x77c/0xef0 fs/fs-writeback.c:1916
 __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:1987
 wb_writeback+0x464/0xba0 fs/fs-writeback.c:2097
 wb_check_old_data_flush fs/fs-writeback.c:2201 [inline]
 wb_do_writeback fs/fs-writeback.c:2254 [inline]
 wb_workfn+0xabc/0xe20 fs/fs-writeback.c:2282
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
task:udevd           state:R  running task     stack:25200 pid:5785  ppid:5142   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x1f2/0x410 kernel/locking/lockdep.c:5758
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 66 43 c7 44 3c 09 00 00 43 c6 44 3c 0b 00
RSP: 0018:ffffc900044ef9e0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: bc7092d785b91c00
RDX: 0000000000000000 RSI: ffffffff8aaac440 RDI: ffffffff8afc6900
RBP: ffffc900044efae8 R08: dffffc0000000000 R09: 1ffffffff21b0aa4
R10: dffffc0000000000 R11: fffffbfff21b0aa5 R12: 1ffff9200089df48
R13: ffffffff8cd2f760 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 aa_file_perm+0x13d/0xec0 security/apparmor/file.c:598
 common_file_perm+0x18e/0x1f0 security/apparmor/lsm.c:522
 security_file_permission+0x69/0xa0 security/security.c:2585
 rw_verify_area fs/read_write.c:374 [inline]
 vfs_read+0x1d3/0x920 fs/read_write.c:461
 ksys_read+0x147/0x250 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f7f5f2a7407
RSP: 002b:00007ffdd97d2390 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f7f5f9f7880 RCX: 00007f7f5f2a7407
RDX: 0000000000000080 RSI: 00007ffdd97d24d0 RDI: 0000000000000003
RBP: 000055848b283910 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffdd97d2420
R13: 00007ffdd97d2420 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10570 jiffies! g12353 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:26920 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </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: 5929 Comm: syz.0.19 Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:preempt_count_add+0x6a/0x1a0 kernel/sched/core.c:5849
Code: a8 7e 48 c7 c0 80 c4 e8 96 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 e6 00 00 00 83 3d cf 61 8d 15 00 75 11 65 8b 05 4e 57 a8 7e <0f> b6 c0 3d f5 00 00 00 73 58 65 8b 05 3d 57 a8 7e 25 ff ff ff 7f
RSP: 0018:ffffc900001f0858 EFLAGS: 00000046
RAX: 0000000080010004 RBX: 1ffff9200003e129 RCX: ffffffff96e8c403
RDX: ffff888077359e00 RSI: 0000000000000002 RDI: 0000000000000001
RBP: 0000000000000002 R08: ffffc900001f0a10 R09: 000000000000000a
R10: 0000000000000004 R11: 0000000000010000 R12: ffffc900001f0948
R13: dffffc0000000000 R14: ffffc900001f0980 R15: dffffc0000000000
FS:  00007f71626e16c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f71626bff40 CR3: 000000002fc5f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 unwind_next_frame+0xbe/0x2970 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
 __sigqueue_alloc+0x40c/0x520 kernel/signal.c:438
 __send_signal_locked+0x22f/0xe00 kernel/signal.c:1130
 do_send_sig_info kernel/signal.c:1312 [inline]
 group_send_sig_info+0x1fa/0x260 kernel/signal.c:1462
 do_bpf_send_signal+0x7f/0x190 kernel/trace/bpf_trace.c:836
 irq_work_single+0xd5/0x230 kernel/irq_work.c:221
 irq_work_run_list kernel/irq_work.c:252 [inline]
 irq_work_run+0x156/0x2e0 kernel/irq_work.c:261
 __sysvec_irq_work+0x98/0x380 arch/x86/kernel/irq_work.c:22
 instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
 sysvec_irq_work+0x9c/0xc0 arch/x86/kernel/irq_work.c:17
 </IRQ>
 <TASK>
 asm_sysvec_irq_work+0x1a/0x20 arch/x86/include/asm/idtentry.h:723
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsr arch/x86/include/asm/msr.h:254 [inline]
RIP: 0010:native_apic_msr_write+0x39/0x50 arch/x86/include/asm/apic.h:196
Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 f3 0f 1e fa 89 f6 31 d2 e9 37 7c 19 03 0f 1f 80 00 00 00
RSP: 0018:ffffc9000473fcd8 EFLAGS: 00000246
RAX: 00000000000000f6 RBX: 0000000000000200 RCX: 000000000000083f
RDX: 0000000000000000 RSI: 00000000000000f6 RDI: 000000000000083f
RBP: 0000000000000000 R08: ffffc9000473fc47 R09: 1ffff920008e7f88
R10: dffffc0000000000 R11: fffff520008e7f89 R12: ffff8880b8f35201
R13: dffffc0000000000 R14: ffff8880b8f35290 R15: 0000000000000020
 __apic_send_IPI_self arch/x86/include/asm/apic.h:454 [inline]
 arch_irq_work_raise+0x68/0x70 arch/x86/kernel/irq_work.c:31
 irq_work_queue+0x99/0x140 kernel/irq_work.c:124
 bpf_send_signal_common+0x2b6/0x420 kernel/trace/bpf_trace.c:875
 ____bpf_send_signal kernel/trace/bpf_trace.c:884 [inline]
 bpf_send_signal+0x19/0x20 kernel/trace/bpf_trace.c:882
 bpf_prog_7ba5217f62dcd359+0x40/0x44
 bpf_dispatcher_nop_func include/linux/bpf.h:1213 [inline]
 __bpf_prog_run include/linux/filter.h:612 [inline]
 bpf_prog_run include/linux/filter.h:619 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
 bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
 trace_sys_enter+0x69/0x80 include/trace/events/syscalls.h:18
 syscall_trace_enter+0xf0/0x150 kernel/entry/common.c:81
 do_syscall_64+0x28/0xb0 arch/x86/entry/common.c:77
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f716172ab19
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007f71626e0b40 EFLAGS: 00000246 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 00007f71619b5fa8 RCX: 00007f716172ab19
RDX: 00007f71626e0b40 RSI: 00007f71626e0c70 RDI: 0000000000000011
RBP: 00007f71619b5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f71619b5fac
R13: 0000000000000000 R14: 00007ffdde5c06b0 R15: 00007ffdde5c0798
 </TASK>
sched: RT throttling activated