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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getpage_gfp

read-write to 0xffff888139996570 of 8 bytes by task 12350 on cpu 1:
 shmem_add_to_page_cache+0x802/0x8f0 mm/shmem.c:745
 shmem_getpage_gfp+0x7af/0x1750 mm/shmem.c:1938
 shmem_fault+0xd2/0x350 mm/shmem.c:2115
 __do_fault mm/memory.c:4165 [inline]
 do_read_fault mm/memory.c:4514 [inline]
 do_fault+0x500/0xb20 mm/memory.c:4643
 handle_pte_fault mm/memory.c:4907 [inline]
 __handle_mm_fault mm/memory.c:5046 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5144
 faultin_page mm/gup.c:955 [inline]
 __get_user_pages+0x34a/0xbf0 mm/gup.c:1176
 populate_vma_page_range mm/gup.c:1520 [inline]
 __mm_populate+0x26e/0x3a0 mm/gup.c:1633
 mm_populate include/linux/mm.h:2710 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:557
 ksys_mmap_pgoff+0xc2/0x320 mm/mmap.c:1633
 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 0xffff888139996570 of 8 bytes by task 12340 on cpu 0:
 shmem_recalc_inode mm/shmem.c:362 [inline]
 shmem_getpage_gfp+0xd8b/0x1750 mm/shmem.c:1948
 shmem_fault+0xd2/0x350 mm/shmem.c:2115
 __do_fault mm/memory.c:4165 [inline]
 do_read_fault mm/memory.c:4514 [inline]
 do_fault+0x500/0xb20 mm/memory.c:4643
 handle_pte_fault mm/memory.c:4907 [inline]
 __handle_mm_fault mm/memory.c:5046 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5144
 do_user_addr_fault+0x4cd/0x940 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1484 [inline]
 exc_page_fault+0x60/0x160 arch/x86/mm/fault.c:1540
 asm_exc_page_fault+0x22/0x30
 fault_in_readable+0x115/0x1a0
 fault_in_iov_iter_readable+0xd7/0x140 lib/iov_iter.c:290
 generic_perform_write+0x116/0x3f0 mm/filemap.c:3734
 ext4_buffered_write_iter+0x235/0x3e0 fs/ext4/file.c:270
 ext4_file_write_iter+0x2e3/0x1210
 call_write_iter include/linux/fs.h:2188 [inline]
 new_sync_write fs/read_write.c:493 [inline]
 vfs_write+0x471/0x770 fs/read_write.c:580
 ksys_write+0xe8/0x1a0 fs/read_write.c:633
 __do_sys_write fs/read_write.c:645 [inline]
 __se_sys_write fs/read_write.c:642 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:642
 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: 0x000000000000002f -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12340 Comm: syz-executor.0 Not tainted 5.19.0-syzkaller-07280-gb44f2fd87919-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
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