==================================================================
BUG: KCSAN: data-race in next_uptodate_page / shmem_write_end

write to 0xffff88812a2947b8 of 8 bytes by task 9385 on cpu 1:
 i_size_write include/linux/fs.h:889 [inline]
 shmem_write_end+0x59/0x380 mm/shmem.c:2496
 generic_perform_write+0x264/0x3f0 mm/filemap.c:3790
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3907
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3939
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:868
 vfs_iter_write+0x4c/0x70 fs/read_write.c:909
 iter_file_splice_write+0x44a/0x7c0 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3bf/0x910 fs/read_write.c:1262
 __do_sys_sendfile64 fs/read_write.c:1324 [inline]
 __se_sys_sendfile64 fs/read_write.c:1316 [inline]
 __x64_sys_sendfile64+0xb9/0x150 fs/read_write.c:1316
 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 0xffff88812a2947b8 of 8 bytes by task 9398 on cpu 0:
 i_size_read include/linux/fs.h:867 [inline]
 next_uptodate_page+0x26f/0x4e0 mm/filemap.c:3321
 next_map_page mm/filemap.c:3346 [inline]
 filemap_map_pages+0x9d1/0xae0 mm/filemap.c:3418
 do_fault_around mm/memory.c:4483 [inline]
 do_read_fault mm/memory.c:4509 [inline]
 do_fault+0x433/0xb20 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
 strncpy_from_user+0xd4/0x230 lib/strncpy_from_user.c:139
 getname_flags+0xb0/0x350 fs/namei.c:150
 getname fs/namei.c:218 [inline]
 __do_sys_mkdir fs/namei.c:4021 [inline]
 __se_sys_mkdir fs/namei.c:4019 [inline]
 __x64_sys_mkdir+0x31/0x50 fs/namei.c:4019
 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: 0x0000000000003498 -> 0x00000000000034e0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9398 Comm: syz-executor.5 Not tainted 5.19.0-syzkaller-00428-g9de1f9c8ca51-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
==================================================================