syzbot

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BUG: KMSAN: uninit-value in rcu_cpu_has_callbacks kernel/rcu/tree.c:3420 [inline]
BUG: KMSAN: uninit-value in rcu_needs_cpu+0x160/0x1d0 kernel/rcu/tree_plugin.h:1314
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.17.0+ #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1091
 __msan_warning_32+0x70/0xc0 mm/kmsan/kmsan_instr.c:620
 rcu_cpu_has_callbacks kernel/rcu/tree.c:3420 [inline]
 rcu_needs_cpu+0x160/0x1d0 kernel/rcu/tree_plugin.h:1314
 tick_nohz_next_event+0x24f/0x790 kernel/time/tick-sched.c:672
 __tick_nohz_idle_stop_tick kernel/time/tick-sched.c:930 [inline]
 tick_nohz_idle_stop_tick+0x13e/0xd60 kernel/time/tick-sched.c:960
 cpuidle_idle_call kernel/sched/idle.c:150 [inline]
 do_idle+0x279/0x830 kernel/sched/idle.c:262
 cpu_startup_entry+0x45/0x50 kernel/sched/idle.c:368
 start_secondary+0x3c6/0x490 arch/x86/kernel/smpboot.c:272
 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:294 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:685
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:464
 rcu_segcblist_enqueue+0x24c/0x2d0 kernel/rcu/rcu_segcblist.c:150
 __call_rcu+0x227/0xef0 kernel/rcu/tree.c:3057
 call_rcu_sched+0x32/0x40 kernel/rcu/tree.c:3097
 free_pid+0x441/0x450 kernel/pid.c:156
 __change_pid kernel/pid.c:294 [inline]
 detach_pid+0x35a/0x370 kernel/pid.c:299
 __unhash_process kernel/exit.c:75 [inline]
 __exit_signal kernel/exit.c:156 [inline]
 release_task+0x10a0/0x2530 kernel/exit.c:200
 exit_notify kernel/exit.c:736 [inline]
 do_exit+0x2e11/0x3930 kernel/exit.c:887
 do_group_exit+0x1a0/0x360 kernel/exit.c:970
 get_signal+0x1405/0x1ec0 kernel/signal.c:2482
 do_signal+0xb8/0x1d20 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:162 [inline]
 prepare_exit_to_usermode+0x271/0x3a0 arch/x86/entry/common.c:196
 syscall_return_slowpath+0xe9/0x710 arch/x86/entry/common.c:265
 do_syscall_64+0x1ad/0x230 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Local variable description: ----tlb.i@ldt_arch_exit_mmap
Variable was created at:
 ldt_arch_exit_mmap+0x46/0x160 arch/x86/kernel/ldt.c:302
 arch_exit_mmap arch/x86/include/asm/mmu_context.h:245 [inline]
 exit_mmap+0x410/0x980 mm/mmap.c:3094
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