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BUG: KMSAN: uninit-value in __call_rcu+0x4b8/0xef0 kernel/rcu/tree.c:3035
CPU: 1 PID: 4526 Comm: syz-executor1 Not tainted 4.17.0+ #9
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:1125
 __msan_warning_32+0x70/0xc0 mm/kmsan/kmsan_instr.c:620
 __call_rcu+0x4b8/0xef0 kernel/rcu/tree.c:3035
 call_rcu_sched+0x32/0x40 kernel/rcu/tree.c:3097
 radix_tree_node_free lib/radix-tree.c:455 [inline]
 delete_node+0x3cf/0xc80 lib/radix-tree.c:785
 __radix_tree_delete+0x122d/0x1300 lib/radix-tree.c:1999
 radix_tree_delete_item+0x629/0x870 lib/radix-tree.c:2050
 idr_remove+0xa4/0xc0 lib/idr.c:157
 free_pid+0x2e0/0x450 kernel/pid.c:152
 __change_pid kernel/pid.c:294 [inline]
 detach_pid+0x35a/0x370 kernel/pid.c:299
 __unhash_process kernel/exit.c:77 [inline]
 __exit_signal kernel/exit.c:156 [inline]
 release_task+0x10e0/0x2530 kernel/exit.c:200
 wait_task_zombie kernel/exit.c:1163 [inline]
 wait_consider_task+0x2e4d/0x4550 kernel/exit.c:1390
 do_wait_thread kernel/exit.c:1453 [inline]
 do_wait+0x60b/0xbd0 kernel/exit.c:1524
 kernel_wait4+0x337/0x4b0 kernel/exit.c:1667
 __do_sys_wait4 kernel/exit.c:1679 [inline]
 __se_sys_wait4 kernel/exit.c:1675 [inline]
 __x64_sys_wait4+0x17c/0x320 kernel/exit.c:1675
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x40fd9a
RSP: 002b:0000000000a3eab8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 000000000005995b RCX: 000000000040fd9a
RDX: 0000000040000001 RSI: 0000000000a3ead4 RDI: ffffffffffffffff
RBP: 0000000000000000 R08: 0000000000000001 R09: 00000000024e4940
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000010
R13: 00000000000004b5 R14: 0000000000a3f160 R15: 000000000005957d

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:282 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:297 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:689
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:464
 rcu_segcblist_enqueue+0x275/0x2d0 kernel/rcu/rcu_segcblist.c:151
 __call_rcu+0x227/0xef0 kernel/rcu/tree.c:3057
 call_rcu_sched+0x32/0x40 kernel/rcu/tree.c:3097
 release_task+0x24b9/0x2530 kernel/exit.c:223
 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: ----name.i@proc_flush_task
Variable was created at:
 proc_flush_task+0x60/0x810 fs/proc/base.c:3126
 release_task+0xa1/0x2530 kernel/exit.c:196
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