syzbot

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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff88811c1cf158 of 8 bytes by task 3927 on cpu 0:
 shmem_fallocate+0x301/0x840 mm/shmem.c:3688
 vfs_fallocate+0x3b6/0x400 fs/open.c:342
 madvise_remove mm/madvise.c:1049 [inline]
 madvise_vma_behavior+0x1920/0x1cf0 mm/madvise.c:1346
 madvise_walk_vmas mm/madvise.c:1669 [inline]
 madvise_do_behavior+0x5b7/0x970 mm/madvise.c:1885
 do_madvise+0x10e/0x190 mm/madvise.c:1978
 __do_sys_madvise mm/madvise.c:1987 [inline]
 __se_sys_madvise mm/madvise.c:1985 [inline]
 __x64_sys_madvise+0x64/0x80 mm/madvise.c:1985
 x64_sys_call+0x1f1a/0x3000 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811c1cf158 of 8 bytes by task 3928 on cpu 1:
 shmem_fault+0x90/0x250 mm/shmem.c:2727
 __do_fault+0xbc/0x200 mm/memory.c:5280
 do_read_fault mm/memory.c:5698 [inline]
 do_fault mm/memory.c:5832 [inline]
 do_pte_missing mm/memory.c:4361 [inline]
 handle_pte_fault mm/memory.c:6177 [inline]
 __handle_mm_fault mm/memory.c:6318 [inline]
 handle_mm_fault+0xf78/0x2be0 mm/memory.c:6487
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0x102a/0x1ed0 mm/gup.c:1428
 populate_vma_page_range mm/gup.c:1860 [inline]
 __mm_populate+0x243/0x3a0 mm/gup.c:1963
 mm_populate include/linux/mm.h:3471 [inline]
 vm_mmap_pgoff+0x232/0x2e0 mm/util.c:586
 ksys_mmap_pgoff+0xc2/0x310 mm/mmap.c:604
 x64_sys_call+0x14a3/0x3000 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffc90000f23b58 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3928 Comm: syz.2.84 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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