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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getpage_gfp

read-write to 0xffff8881313e7ee8 of 8 bytes by task 3043 on cpu 0:
 shmem_add_to_page_cache+0x802/0x8e0 mm/shmem.c:746
 shmem_getpage_gfp+0x7af/0x1750 mm/shmem.c:1948
 shmem_fault+0xd2/0x350 mm/shmem.c:2125
 __do_fault mm/memory.c:4173 [inline]
 do_read_fault mm/memory.c:4518 [inline]
 do_fault+0x500/0xb20 mm/memory.c:4647
 handle_pte_fault mm/memory.c:4911 [inline]
 __handle_mm_fault mm/memory.c:5053 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5151
 faultin_page mm/gup.c:955 [inline]
 __get_user_pages+0x328/0xc00 mm/gup.c:1195
 populate_vma_page_range mm/gup.c:1552 [inline]
 __mm_populate+0x26e/0x3a0 mm/gup.c:1665
 mm_populate include/linux/mm.h:2656 [inline]
 __do_sys_remap_file_pages+0x39c/0x590 mm/mmap.c:2959
 __se_sys_remap_file_pages mm/mmap.c:2888 [inline]
 __x64_sys_remap_file_pages+0x63/0x70 mm/mmap.c:2888
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881313e7ee8 of 8 bytes by task 3040 on cpu 1:
 shmem_recalc_inode mm/shmem.c:363 [inline]
 shmem_getpage_gfp+0xd8b/0x1750 mm/shmem.c:1958
 shmem_fault+0xd2/0x350 mm/shmem.c:2125
 __do_fault mm/memory.c:4173 [inline]
 do_shared_fault mm/memory.c:4573 [inline]
 do_fault+0x5df/0xb20 mm/memory.c:4651
 handle_pte_fault mm/memory.c:4911 [inline]
 __handle_mm_fault mm/memory.c:5053 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5151
 do_user_addr_fault+0x4a1/0x980 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1488 [inline]
 exc_page_fault+0x60/0x160 arch/x86/mm/fault.c:1544
 asm_exc_page_fault+0x22/0x30
 copy_user_enhanced_fast_string+0xa/0x40
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 copyout+0x72/0x90 lib/iov_iter.c:170
 _copy_to_iter+0x261/0x8b0 lib/iov_iter.c:524
 copy_page_to_iter+0x333/0x3f0 lib/iov_iter.c:722
 process_vm_rw_pages mm/process_vm_access.c:45 [inline]
 process_vm_rw_single_vec+0x298/0x440 mm/process_vm_access.c:117
 process_vm_rw_core mm/process_vm_access.c:215 [inline]
 process_vm_rw+0x3e1/0x570 mm/process_vm_access.c:283
 __do_sys_process_vm_readv mm/process_vm_access.c:295 [inline]
 __se_sys_process_vm_readv mm/process_vm_access.c:291 [inline]
 __x64_sys_process_vm_readv+0x76/0x90 mm/process_vm_access.c:291
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000000030b -> 0x000000000000030c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3040 Comm: syz-executor.0 Not tainted 5.19.0-syzkaller-13215-geb555cb5b794-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
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