syzbot

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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff88811f1582d8 of 8 bytes by task 4739 on cpu 1:
 shmem_fallocate+0x28f/0x920 mm/shmem.c:3720
 vfs_fallocate+0x3b6/0x450 fs/open.c:340
 madvise_remove mm/madvise.c:1044 [inline]
 madvise_vma_behavior+0x2a1/0x20c0 mm/madvise.c:1358
 madvise_walk_vmas mm/madvise.c:1719 [inline]
 madvise_do_behavior+0x5de/0xa10 mm/madvise.c:1935
 do_madvise+0x10e/0x190 mm/madvise.c:2028
 __do_sys_madvise mm/madvise.c:2037 [inline]
 __se_sys_madvise mm/madvise.c:2035 [inline]
 __x64_sys_madvise+0x63/0x80 mm/madvise.c:2035
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811f1582d8 of 8 bytes by task 4737 on cpu 0:
 shmem_fault+0x90/0x250 mm/shmem.c:2761
 __do_fault+0xbc/0x200 mm/memory.c:5355
 do_shared_fault mm/memory.c:5854 [inline]
 do_fault mm/memory.c:5928 [inline]
 do_pte_missing mm/memory.c:4469 [inline]
 handle_pte_fault mm/memory.c:6308 [inline]
 __handle_mm_fault mm/memory.c:6446 [inline]
 handle_mm_fault+0xfa1/0x3020 mm/memory.c:6615
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0x1023/0x1ea0 mm/gup.c:1428
 __get_user_pages_locked mm/gup.c:1692 [inline]
 faultin_page_range+0x107/0x4d0 mm/gup.c:1912
 madvise_populate mm/madvise.c:974 [inline]
 madvise_do_behavior+0x19f/0xa10 mm/madvise.c:1933
 do_madvise+0x10e/0x190 mm/madvise.c:2028
 __do_sys_madvise mm/madvise.c:2037 [inline]
 __se_sys_madvise mm/madvise.c:2035 [inline]
 __x64_sys_madvise+0x63/0x80 mm/madvise.c:2035
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffffc9000138bb40

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4737 Comm: syz.4.339 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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