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BUG: KCSAN: data-race in shmem_fallocate / shmem_fault

write to 0xffff88813973fda0 of 8 bytes by task 19601 on cpu 1:
 shmem_fallocate+0x32f/0x860 mm/shmem.c:3080
 vfs_fallocate+0x378/0x3e0 fs/open.c:324
 madvise_remove mm/madvise.c:990 [inline]
 madvise_vma_behavior mm/madvise.c:1014 [inline]
 madvise_walk_vmas mm/madvise.c:1249 [inline]
 do_madvise+0x741/0x26f0 mm/madvise.c:1429
 __do_sys_madvise mm/madvise.c:1442 [inline]
 __se_sys_madvise mm/madvise.c:1440 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1440
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88813973fda0 of 8 bytes by task 19592 on cpu 0:
 shmem_fault+0x9d/0x250 mm/shmem.c:2206
 __do_fault mm/memory.c:4265 [inline]
 do_shared_fault mm/memory.c:4692 [inline]
 do_fault mm/memory.c:4766 [inline]
 do_pte_missing mm/memory.c:3730 [inline]
 handle_pte_fault mm/memory.c:5038 [inline]
 __handle_mm_fault mm/memory.c:5179 [inline]
 handle_mm_fault+0x17db/0x2dd0 mm/memory.c:5344
 do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x2f7/0x6c0 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
 rep_movs_alternative+0x4a/0x70 arch/x86/lib/copy_user_64.S:65
 copy_user_generic arch/x86/include/asm/uaccess_64.h:112 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:133 [inline]
 copy_to_user_iter lib/iov_iter.c:25 [inline]
 iterate_ubuf include/linux/iov_iter.h:29 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
 iterate_and_advance include/linux/iov_iter.h:271 [inline]
 _copy_to_iter+0x137/0xb20 lib/iov_iter.c:186
 copy_to_iter include/linux/uio.h:197 [inline]
 get_random_bytes_user+0x112/0x260 drivers/char/random.c:451
 __do_sys_getrandom drivers/char/random.c:1391 [inline]
 __se_sys_getrandom drivers/char/random.c:1364 [inline]
 __x64_sys_getrandom+0xcd/0x1a0 drivers/char/random.c:1364
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffffc9000e17bcd0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19592 Comm: syz-executor.1 Not tainted 6.6.0-syzkaller-15494-g6bc986ab839c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
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