syzbot

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BUG: KCSAN: data-race in __fat_write_inode / _copy_to_iter

write to 0xffff88811dfc763c of 4 bytes by task 12745 on cpu 1:
 __fat_write_inode+0x244/0x4e0 fs/fat/inode.c:885
 fat_write_inode+0xb9/0xd0 fs/fat/inode.c:919
 write_inode+0x89/0x1f0 fs/fs-writeback.c:1440
 __writeback_single_inode+0x2c6/0x590 fs/fs-writeback.c:1652
 writeback_single_inode+0x126/0x4f0 fs/fs-writeback.c:1708
 sync_inode_metadata+0x52/0x70 fs/fs-writeback.c:2743
 __generic_file_fsync+0xf5/0x140 fs/libfs.c:1126
 fat_file_fsync+0x48/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x107/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2869 [inline]
 generic_file_write_iter+0x18d/0x1c0 mm/filemap.c:3902
 do_iter_write+0x494/0x750 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x44a/0x7c0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:931
 splice_direct_to_actor+0x305/0x620 fs/splice.c:886
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1303 [inline]
 __x64_sys_sendfile64+0xb9/0x150 fs/read_write.c:1303
 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 0xffff88811dfc7000 of 4096 bytes by task 2871 on cpu 0:
 instrument_copy_to_user include/linux/instrumented.h:119 [inline]
 copyout lib/iov_iter.c:169 [inline]
 _copy_to_iter+0x11d/0x8b0 lib/iov_iter.c:524
 copy_page_to_iter+0x333/0x3f0 lib/iov_iter.c:722
 copy_folio_to_iter include/linux/uio.h:169 [inline]
 filemap_read+0x119b/0x1430 mm/filemap.c:2711
 blkdev_read_iter+0x2c6/0x370 block/fops.c:598
 call_read_iter include/linux/fs.h:2181 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3a5/0x560 fs/read_write.c:470
 ksys_read+0xe8/0x1a0 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2871 Comm: udevd Not tainted 6.0.0-rc5-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
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