syzbot

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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff88813b9988c8 of 8 bytes by task 29770 on cpu 0:
 shmem_fallocate+0x252/0x8d0 mm/shmem.c:2773
 vfs_fallocate+0x369/0x3d0 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+0x77b/0x28a0 mm/madvise.c:1439
 __do_sys_madvise mm/madvise.c:1452 [inline]
 __se_sys_madvise mm/madvise.c:1450 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1450
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813b9988c8 of 8 bytes by task 29772 on cpu 1:
 shmem_fault+0x93/0x3d0 mm/shmem.c:2110
 __do_fault mm/memory.c:4141 [inline]
 do_read_fault mm/memory.c:4492 [inline]
 do_fault mm/memory.c:4621 [inline]
 handle_pte_fault mm/memory.c:4909 [inline]
 __handle_mm_fault mm/memory.c:5051 [inline]
 handle_mm_fault+0x115d/0x21d0 mm/memory.c:5197
 faultin_page mm/gup.c:925 [inline]
 __get_user_pages+0x363/0xc30 mm/gup.c:1147
 populate_vma_page_range mm/gup.c:1543 [inline]
 __mm_populate+0x23a/0x360 mm/gup.c:1652
 mm_populate include/linux/mm.h:3026 [inline]
 vm_mmap_pgoff+0x174/0x210 mm/util.c:547
 ksys_mmap_pgoff+0xc5/0x320 mm/mmap.c:1410
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000000 -> 0xffffc90000ee7ce0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29772 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-00034-gfcd476ea6a88 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/17/2023
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