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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_get_folio_gfp

read-write to 0xffff8881250c0870 of 8 bytes by task 25680 on cpu 0:
 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_read_fault mm/memory.c:4547 [inline]
 do_fault mm/memory.c:4670 [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+0x1224/0x2c10 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+0x30/0xb0 arch/x86/lib/copy_user_64.S:50
 copy_user_generic arch/x86/include/asm/uaccess_64.h:112 [inline]
 raw_copy_from_user arch/x86/include/asm/uaccess_64.h:127 [inline]
 _copy_from_user+0x80/0xd0 lib/usercopy.c:23
 copy_from_user include/linux/uaccess.h:183 [inline]
 copy_msghdr_from_user+0x54/0x2a0 net/socket.c:2424
 recvmsg_copy_msghdr net/socket.c:2679 [inline]
 ___sys_recvmsg net/socket.c:2751 [inline]
 do_recvmmsg+0x290/0x720 net/socket.c:2849
 __sys_recvmmsg net/socket.c:2928 [inline]
 __do_sys_recvmmsg net/socket.c:2951 [inline]
 __se_sys_recvmmsg net/socket.c:2944 [inline]
 __x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2944
 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 0xffff8881250c0870 of 8 bytes by task 25686 on cpu 1:
 shmem_recalc_inode mm/shmem.c:360 [inline]
 shmem_get_folio_gfp+0xe1e/0x1200 mm/shmem.c:1988
 shmem_fault+0xe6/0x3f0 mm/shmem.c:2163
 __do_fault mm/memory.c:4198 [inline]
 do_read_fault mm/memory.c:4547 [inline]
 do_fault mm/memory.c:4670 [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+0x1224/0x2c10 mm/memory.c:5233
 faultin_page mm/gup.c:959 [inline]
 __get_user_pages+0x42e/0xd20 mm/gup.c:1258
 populate_vma_page_range mm/gup.c:1649 [inline]
 __mm_populate+0x23b/0x360 mm/gup.c:1758
 mm_populate include/linux/mm.h:3213 [inline]
 __do_sys_remap_file_pages mm/mmap.c:3004 [inline]
 __se_sys_remap_file_pages+0x447/0x580 mm/mmap.c:2930
 __x64_sys_remap_file_pages+0x67/0x80 mm/mmap.c:2930
 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: 0x00000000000000fd -> 0x00000000000000fe

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25686 Comm: syz-executor.0 Not tainted 6.5.0-rc6-syzkaller-00225-gaa9ea98cca3a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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