EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
EXT4-fs error (device loop2): ext4_mb_mark_diskspace_used:4113: comm syz.2.2952: Allocating blocks 385-513 which overlap fs metadata
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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff888119cc0b90 of 8 bytes by task 11896 on cpu 0:
 shmem_fallocate+0x221/0x840 mm/shmem.c:3678
 vfs_fallocate+0x410/0x450 fs/open.c:338
 madvise_remove mm/madvise.c:1034 [inline]
 madvise_vma_behavior mm/madvise.c:1263 [inline]
 madvise_walk_vmas mm/madvise.c:1530 [inline]
 madvise_do_behavior+0x1106/0x24a0 mm/madvise.c:1695
 do_madvise mm/madvise.c:1782 [inline]
 __do_sys_madvise mm/madvise.c:1790 [inline]
 __se_sys_madvise mm/madvise.c:1788 [inline]
 __x64_sys_madvise+0xc9/0x100 mm/madvise.c:1788
 x64_sys_call+0x2455/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:29
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888119cc0b90 of 8 bytes by task 11890 on cpu 1:
 shmem_fault+0x90/0x250 mm/shmem.c:2727
 __do_fault+0xb9/0x200 mm/memory.c:5098
 do_read_fault mm/memory.c:5518 [inline]
 do_fault mm/memory.c:5652 [inline]
 do_pte_missing mm/memory.c:4160 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault mm/memory.c:6140 [inline]
 handle_mm_fault+0x110c/0x2ae0 mm/memory.c:6309
 faultin_page mm/gup.c:1193 [inline]
 __get_user_pages+0xde2/0x1d20 mm/gup.c:1491
 populate_vma_page_range mm/gup.c:1929 [inline]
 __mm_populate+0x243/0x3a0 mm/gup.c:2032
 mm_populate include/linux/mm.h:3487 [inline]
 vm_mmap_pgoff+0x232/0x2e0 mm/util.c:584
 ksys_mmap_pgoff+0xc2/0x310 mm/mmap.c:607
 x64_sys_call+0x1602/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffffc9000f07bca0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 11890 Comm: syz.2.2952 Not tainted 6.15.0-rc5-syzkaller-00204-g0e1329d4045c #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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