syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5887/1:b..l P4257/1:b..l
	(detected by 0, t=10502 jiffies, g=17685, q=407 ncpus=2)
task:udevd           state:R  running task     stack:24192 pid:4257  ppid:3637   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x80 kernel/kcov.c:314
Code: 28 4d 39 ca 77 22 89 ff 89 f6 49 ff c0 4c 89 01 48 c7 44 11 08 03 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 <48> 8b 04 24 65 48 8b 15 c4 98 81 7e 65 8b 0d c5 98 81 7e 81 e1 00
RSP: 0018:ffffc900041576d8 EFLAGS: 00000206
RAX: 0000000000000300 RBX: 0000000000000300 RCX: dffffc0000000000
RDX: ffff88802e7cd940 RSI: 0000000000000300 RDI: 0000000000000300
RBP: ffffc900041578b0 R08: ffff88802e7cd940 R09: 0000000000000004
R10: 0000000000000003 R11: 0000000000000000 R12: 00007f90289fefff
R13: ffffffff8bb159c1 R14: ffff88807ab54380 R15: 0000000000000005
 mt_external_lock include/linux/maple_tree.h:561 [inline]
 mt_locked lib/maple_tree.c:807 [inline]
 mt_slot lib/maple_tree.c:814 [inline]
 mas_slot lib/maple_tree.c:847 [inline]
 mas_get_slot lib/maple_tree.c:6678 [inline]
 mas_validate_gaps lib/maple_tree.c:6976 [inline]
 mt_validate+0x2d06/0x4c90 lib/maple_tree.c:7244
 validate_mm_mt+0xcd/0x420 mm/mmap.c:295
 validate_mm+0xcc/0x2b0 mm/mmap.c:332
 mmap_region+0x780/0x1c70 mm/mmap.c:2922
 do_mmap+0x958/0xfd0 mm/mmap.c:1436
 vm_mmap_pgoff+0x1b2/0x2b0 mm/util.c:520
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9029049822
RSP: 002b:00007ffc06dade68 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9029049822
RDX: 0000000000000003 RSI: 0000000000000200 RDI: 0000000000000000
RBP: 0000000000000022 R08: 00000000ffffffff R09: 0000000000000000
R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000002600 R14: 000055afb7753cb0 R15: 0000000000010000
 </TASK>
task:syz.1.393       state:R  running task     stack:23808 pid:5887  ppid:4268   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_notrace+0xca/0x110 kernel/sched/core.c:6823
 preempt_schedule_notrace_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
 rcu_lockdep_current_cpu_online+0xfe/0x120 kernel/rcu/tree.c:778
 rcu_read_lock_held_common kernel/rcu/update.c:112 [inline]
 rcu_read_lock_held+0x1a/0x40 kernel/rcu/update.c:309
 xa_entry include/linux/xarray.h:1198 [inline]
 xas_descend+0x129/0x490 lib/xarray.c:204
 xas_load+0xba/0x140 lib/xarray.c:242
 mapping_get_entry mm/filemap.c:1881 [inline]
 __filemap_get_folio+0x1bb/0xdd0 mm/filemap.c:1943
 shmem_get_folio_gfp+0x310/0x3400 mm/shmem.c:1881
 shmem_get_folio mm/shmem.c:2072 [inline]
 shmem_write_begin+0xee/0x3f0 mm/shmem.c:2556
 generic_perform_write+0x2db/0x560 mm/filemap.c:3846
 __generic_file_write_iter+0x172/0x430 mm/filemap.c:3974
 generic_file_write_iter+0xab/0x2e0 mm/filemap.c:4006
 __kernel_write_iter+0x26d/0x630 fs/read_write.c:517
 dump_emit_page fs/coredump.c:950 [inline]
 dump_user_range+0x3ea/0x7f0 fs/coredump.c:977
 elf_core_dump+0x2f77/0x3490 fs/binfmt_elf.c:2354
 do_coredump+0x15ff/0x22b0 fs/coredump.c:824
 get_signal+0x10aa/0x1350 kernel/signal.c:2857
 arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 irqentry_exit_to_user_mode+0x5/0x30 kernel/entry/common.c:316
 exc_page_fault+0x88/0x100 arch/x86/mm/fault.c:1490
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f677c18efd1
RSP: 002b:fffffffffffffe70 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007f677c3e6090 RCX: 00007f677c18efc9
RDX: 0000000000000000 RSI: fffffffffffffe70 RDI: 0000000000008000
RBP: 00007f677c211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f677c3e6128 R14: 00007f677c3e6090 R15: 00007ffec764b098
 </TASK>
rcu: rcu_preempt kthread starved for 9513 jiffies! g17685 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:26912 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741