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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff8881188502d8 of 8 bytes by task 7967 on cpu 1:
 shmem_fallocate+0x320/0x860 mm/shmem.c:3517
 vfs_fallocate+0x368/0x3b0 fs/open.c:327
 madvise_remove mm/madvise.c:1020 [inline]
 madvise_vma_behavior mm/madvise.c:1255 [inline]
 madvise_walk_vmas mm/madvise.c:1497 [inline]
 do_madvise+0x14bd/0x2a70 mm/madvise.c:1684
 __do_sys_madvise mm/madvise.c:1700 [inline]
 __se_sys_madvise mm/madvise.c:1698 [inline]
 __x64_sys_madvise+0x61/0x70 mm/madvise.c:1698
 x64_sys_call+0x23ab/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881188502d8 of 8 bytes by task 7971 on cpu 0:
 shmem_fault+0x97/0x250 mm/shmem.c:2549
 __do_fault+0xb6/0x200 mm/memory.c:4907
 do_read_fault mm/memory.c:5322 [inline]
 do_fault mm/memory.c:5456 [inline]
 do_pte_missing mm/memory.c:3979 [inline]
 handle_pte_fault mm/memory.c:5801 [inline]
 __handle_mm_fault mm/memory.c:5944 [inline]
 handle_mm_fault+0xe98/0x2ac0 mm/memory.c:6112
 faultin_page mm/gup.c:1187 [inline]
 __get_user_pages+0xf2c/0x2670 mm/gup.c:1485
 populate_vma_page_range mm/gup.c:1923 [inline]
 __mm_populate+0x25b/0x3b0 mm/gup.c:2026
 mm_populate include/linux/mm.h:3385 [inline]
 vm_mmap_pgoff+0x1d6/0x290 mm/util.c:593
 ksys_mmap_pgoff+0xd0/0x330 mm/mmap.c:542
 x64_sys_call+0x1940/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffc900038fbca8 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7971 Comm: syz.3.1530 Not tainted 6.12.0-syzkaller-08756-g42d9e8b7ccdd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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