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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff888105d5de88 of 8 bytes by task 30125 on cpu 0:
 shmem_fallocate+0x1fd/0x8e0 mm/shmem.c:2669
 vfs_fallocate+0x459/0x6a0 fs/open.c:307
 madvise_remove+0x126/0x1e0 mm/madvise.c:925
 madvise_vma mm/madvise.c:987 [inline]
 do_madvise+0x5a5/0x1140 mm/madvise.c:1202
 __do_sys_madvise mm/madvise.c:1228 [inline]
 __se_sys_madvise mm/madvise.c:1226 [inline]
 __x64_sys_madvise+0x5d/0x70 mm/madvise.c:1226
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888105d5de88 of 8 bytes by task 30108 on cpu 1:
 shmem_fault+0x8e/0x470 mm/shmem.c:2071
 __do_fault mm/memory.c:3858 [inline]
 do_read_fault mm/memory.c:4173 [inline]
 do_fault mm/memory.c:4301 [inline]
 handle_pte_fault mm/memory.c:4559 [inline]
 __handle_mm_fault mm/memory.c:4694 [inline]
 handle_mm_fault+0xbb7/0x1580 mm/memory.c:4792
 faultin_page mm/gup.c:937 [inline]
 __get_user_pages+0x381/0xc50 mm/gup.c:1158
 populate_vma_page_range mm/gup.c:1490 [inline]
 __mm_populate+0x24d/0x370 mm/gup.c:1599
 mm_populate include/linux/mm.h:2624 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:524
 ksys_mmap_pgoff+0xcf/0x350 mm/mmap.c:1624
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000000000 -> 0xffffc90000c13c70

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30108 Comm: syz-executor.4 Tainted: G        W         5.15.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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