==================================================================
BUG: KCSAN: data-race in filemap_fault / generic_write_end

write to 0xffff888135895cf8 of 8 bytes by task 19560 on cpu 1:
 i_size_write include/linux/fs.h:872 [inline]
 generic_write_end+0x99/0x240 fs/buffer.c:2187
 fat_write_end+0x4a/0x160 fs/fat/inode.c:249
 generic_perform_write+0x23e/0x3a0 mm/filemap.c:3586
 __generic_file_write_iter+0x22d/0x340 mm/filemap.c:3672
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3736
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 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+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888135895cf8 of 8 bytes by task 19565 on cpu 0:
 i_size_read include/linux/fs.h:850 [inline]
 filemap_fault+0x3fe/0xc30 mm/filemap.c:2942
 __do_fault mm/memory.c:3635 [inline]
 do_shared_fault+0xc3/0x680 mm/memory.c:3991
 do_fault mm/memory.c:4069 [inline]
 handle_pte_fault mm/memory.c:4316 [inline]
 __handle_mm_fault mm/memory.c:4451 [inline]
 handle_mm_fault+0x12b0/0x1840 mm/memory.c:4549
 do_user_addr_fault+0x60c/0xc00 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577
 copy_user_enhanced_fast_string+0xe/0x40 arch/x86/lib/copy_user_64.S:205
 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 lib/iov_iter.c:146 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:217 [inline]
 copy_page_to_iter+0x352/0x8a0 lib/iov_iter.c:912
 filemap_read+0x416/0x7b0 mm/filemap.c:2513
 generic_file_read_iter+0x82/0x410 mm/filemap.c:2609
 call_read_iter include/linux/fs.h:1971 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x565/0x5d0 fs/read_write.c:496
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19565 Comm: syz-executor.5 Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================