syzbot

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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff88810522fdc0 of 8 bytes by task 3471 on cpu 0:
 shmem_fallocate+0x28f/0x920 mm/shmem.c:3697
 vfs_fallocate+0x3b6/0x400 fs/open.c:338
 madvise_remove mm/madvise.c:1039 [inline]
 madvise_vma_behavior+0x2a1/0x2100 mm/madvise.c:1352
 madvise_walk_vmas mm/madvise.c:1713 [inline]
 madvise_do_behavior+0x5de/0xa10 mm/madvise.c:1929
 do_madvise+0x10e/0x190 mm/madvise.c:2022
 __do_sys_madvise mm/madvise.c:2031 [inline]
 __se_sys_madvise mm/madvise.c:2029 [inline]
 __x64_sys_madvise+0x63/0x80 mm/madvise.c:2029
 x64_sys_call+0x1eff/0x3020 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810522fdc0 of 8 bytes by task 3472 on cpu 1:
 shmem_fault+0x90/0x250 mm/shmem.c:2758
 __do_fault mm/memory.c:5474 [inline]
 do_read_fault mm/memory.c:5909 [inline]
 do_fault mm/memory.c:6043 [inline]
 do_pte_missing mm/memory.c:4566 [inline]
 handle_pte_fault mm/memory.c:6427 [inline]
 __handle_mm_fault mm/memory.c:6565 [inline]
 handle_mm_fault+0x16cd/0x2e70 mm/memory.c:6734
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0x1290/0x1f10 mm/gup.c:1428
 populate_vma_page_range mm/gup.c:1860 [inline]
 __mm_populate+0x242/0x390 mm/gup.c:1963
 mm_populate include/linux/mm.h:4137 [inline]
 vm_mmap_pgoff+0x23b/0x2d0 mm/util.c:586
 ksys_mmap_pgoff+0xc1/0x310 mm/mmap.c:606
 x64_sys_call+0x14df/0x3020 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffffc90002bcbb48

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3472 Comm: syz.3.9542 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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