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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_recalc_inode

read-write to 0xffff88812a7a8578 of 8 bytes by task 8912 on cpu 1:
 shmem_add_to_page_cache+0x40a/0x510 mm/shmem.c:742
 shmem_get_folio_gfp+0x923/0x1200 mm/shmem.c:1978
 shmem_fault+0xe6/0x3f0 mm/shmem.c:2163
 __do_fault mm/memory.c:4198 [inline]
 do_shared_fault mm/memory.c:4602 [inline]
 do_fault mm/memory.c:4674 [inline]
 do_pte_missing mm/memory.c:3664 [inline]
 handle_pte_fault mm/memory.c:4939 [inline]
 __handle_mm_fault mm/memory.c:5079 [inline]
 handle_mm_fault+0x131b/0x2c10 mm/memory.c:5233
 do_user_addr_fault arch/x86/mm/fault.c:1392 [inline]
 handle_page_fault arch/x86/mm/fault.c:1486 [inline]
 exc_page_fault+0x24d/0x650 arch/x86/mm/fault.c:1542
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
 rep_movs_alternative+0x4a/0xb0 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]
 copyout lib/iov_iter.c:168 [inline]
 _copy_to_iter+0x13c/0x910 lib/iov_iter.c:316
 copy_to_iter include/linux/uio.h:194 [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:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88812a7a8578 of 8 bytes by task 8921 on cpu 0:
 shmem_recalc_inode+0x47/0x170 mm/shmem.c:360
 shmem_swapin_folio+0x899/0xa40 mm/shmem.c:1817
 shmem_get_folio_gfp+0x264/0x1200 mm/shmem.c:1891
 shmem_fault+0xe6/0x3f0 mm/shmem.c:2163
 __do_fault mm/memory.c:4198 [inline]
 do_shared_fault mm/memory.c:4602 [inline]
 do_fault mm/memory.c:4674 [inline]
 do_pte_missing mm/memory.c:3664 [inline]
 handle_pte_fault mm/memory.c:4939 [inline]
 __handle_mm_fault mm/memory.c:5079 [inline]
 handle_mm_fault+0x131b/0x2c10 mm/memory.c:5233
 faultin_page mm/gup.c:959 [inline]
 __get_user_pages+0x42e/0xd20 mm/gup.c:1258
 faultin_vma_page_range+0x7e/0xa0 mm/gup.c:1707
 madvise_populate mm/madvise.c:933 [inline]
 madvise_vma_behavior mm/madvise.c:1042 [inline]
 madvise_walk_vmas mm/madvise.c:1264 [inline]
 do_madvise+0x97c/0x29b0 mm/madvise.c:1444
 __do_sys_madvise mm/madvise.c:1457 [inline]
 __se_sys_madvise mm/madvise.c:1455 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1455
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000000006ab -> 0x00000000000006ac

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8921 Comm: syz-executor.2 Not tainted 6.5.0-rc5-syzkaller-00053-g13b937206866 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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