syzbot

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BUG: KMSAN: uninit-value in ident_p4d_init arch/x86/mm/ident_map.c:74 [inline]
BUG: KMSAN: uninit-value in kernel_ident_mapping_init+0x6f8/0x980 arch/x86/mm/ident_map.c:114
CPU: 0 PID: 4463 Comm: syz-executor832 Not tainted 4.17.0-rc3+ #94
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+0x142/0x240 mm/kmsan/kmsan.c:1084
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
 ident_p4d_init arch/x86/mm/ident_map.c:74 [inline]
 kernel_ident_mapping_init+0x6f8/0x980 arch/x86/mm/ident_map.c:114
 init_pgtable arch/x86/kernel/machine_kexec_64.c:136 [inline]
 machine_kexec_prepare+0x27f/0x11b0 arch/x86/kernel/machine_kexec_64.c:254
 do_kexec_load+0xa59/0xd70 kernel/kexec.c:143
 __do_sys_kexec_load kernel/kexec.c:243 [inline]
 __se_sys_kexec_load kernel/kexec.c:218 [inline]
 __x64_sys_kexec_load+0x355/0x3d0 kernel/kexec.c:218
 do_syscall_64+0x154/0x220 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4400c9
RSP: 002b:00007ffef7e7b3e8 EFLAGS: 00000203 ORIG_RAX: 00000000000000f6
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004400c9
RDX: 00000000200005c0 RSI: 0000000000000007 RDI: 0000000000000000
RBP: 00000000006ca018 R08: 00000000006ca018 R09: 00000000006ca018
R10: 0000000000000000 R11: 0000000000000203 R12: 00000000004015f0
R13: 0000000000401680 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:815
 kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:885
 __alloc_pages_nodemask+0xf8e/0x5dd0 mm/page_alloc.c:4402
 alloc_pages_current+0x6b5/0x970 mm/mempolicy.c:2093
 alloc_pages include/linux/gfp.h:494 [inline]
 kimage_alloc_pages kernel/kexec_core.c:304 [inline]
 kimage_alloc_normal_control_pages kernel/kexec_core.c:378 [inline]
 kimage_alloc_control_pages+0x177/0x1490 kernel/kexec_core.c:485
 kimage_alloc_init kernel/kexec.c:83 [inline]
 do_kexec_load+0x6ae/0xd70 kernel/kexec.c:136
 __do_sys_kexec_load kernel/kexec.c:243 [inline]
 __se_sys_kexec_load kernel/kexec.c:218 [inline]
 __x64_sys_kexec_load+0x355/0x3d0 kernel/kexec.c:218
 do_syscall_64+0x154/0x220 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
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