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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff8881609f0ea0 of 8 bytes by task 12843 on cpu 1:
 shmem_fallocate+0x23e/0x860 mm/shmem.c:3087
 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 0xffff8881609f0ea0 of 8 bytes by task 12840 on cpu 0:
 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
 do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x2f7/0x6c0 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
 rep_movs_alternative+0x15/0x70 arch/x86/lib/copy_user_64.S:43
 copy_user_generic arch/x86/include/asm/uaccess_64.h:112 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:133 [inline]
 _copy_to_user+0x77/0x90 lib/usercopy.c:41
 copy_to_user include/linux/uaccess.h:191 [inline]
 do_timer_create+0x75c/0xa30 kernel/time/posix-timers.c:500
 __se_sys_timer_create kernel/time/posix-timers.c:530 [inline]
 __x64_sys_timer_create+0xbb/0xe0 kernel/time/posix-timers.c:530
 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: 0x0000000000000000 -> 0xffffc90003573cd0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12840 Comm: syz-executor.2 Not tainted 6.7.0-rc7-syzkaller-00003-gfbafc3e621c3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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