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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff8881752a82e0 of 8 bytes by task 25804 on cpu 0:
 shmem_fallocate+0x32f/0x860 mm/shmem.c:3097
 vfs_fallocate+0x378/0x3e0 fs/open.c:324
 madvise_remove mm/madvise.c:1001 [inline]
 madvise_vma_behavior mm/madvise.c:1025 [inline]
 madvise_walk_vmas mm/madvise.c:1260 [inline]
 do_madvise+0x741/0x26f0 mm/madvise.c:1440
 __do_sys_madvise mm/madvise.c:1453 [inline]
 __se_sys_madvise mm/madvise.c:1451 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1451
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881752a82e0 of 8 bytes by task 25784 on cpu 1:
 shmem_fault+0x9d/0x250 mm/shmem.c:2223
 __do_fault mm/memory.c:4266 [inline]
 do_shared_fault mm/memory.c:4693 [inline]
 do_fault mm/memory.c:4767 [inline]
 do_pte_missing mm/memory.c:3731 [inline]
 handle_pte_fault mm/memory.c:5039 [inline]
 __handle_mm_fault mm/memory.c:5180 [inline]
 handle_mm_fault+0x17db/0x2dd0 mm/memory.c:5345
 faultin_page mm/gup.c:956 [inline]
 __get_user_pages+0x402/0xe40 mm/gup.c:1239
 faultin_vma_page_range+0x7e/0xa0 mm/gup.c:1735
 madvise_populate mm/madvise.c:929 [inline]
 madvise_vma_behavior mm/madvise.c:1038 [inline]
 madvise_walk_vmas mm/madvise.c:1260 [inline]
 do_madvise+0x90b/0x26f0 mm/madvise.c:1440
 __do_sys_madvise mm/madvise.c:1453 [inline]
 __se_sys_madvise mm/madvise.c:1451 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1451
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffffc90000ac7cd0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25784 Comm: syz-executor.2 Tainted: G        W          6.7.0-rc6-syzkaller-00168-g9a6b294ab496 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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