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BUG: KCSAN: data-race in mark_buffer_dirty_inode / sync_mapping_buffers

write to 0xffff88813e747948 of 8 bytes by task 14150 on cpu 0:
 __remove_assoc_queue fs/buffer.c:516 [inline]
 fsync_buffers_list fs/buffer.c:784 [inline]
 sync_mapping_buffers+0x165/0x7e0 fs/buffer.c:577
 fat_file_fsync+0xad/0x100 fs/fat/file.c:195
 vfs_fsync_range+0x111/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2734 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4055
 call_write_iter include/linux/fs.h:2087 [inline]
 iter_file_splice_write+0x5de/0x950 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x167/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x2fb/0x660 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88813e747948 of 8 bytes by task 14117 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:680
 fat16_ent_put+0x4f/0x60 fs/fat/fatent.c:184
 fat_alloc_clusters+0x4b5/0xa60 fs/fat/fatent.c:503
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x25c/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x40b/0xf80 fs/buffer.c:2103
 __block_write_begin fs/buffer.c:2152 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2211
 cont_write_begin+0x479/0x690 fs/buffer.c:2565
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1c9/0x410 mm/filemap.c:3930
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4025
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4051
 call_write_iter include/linux/fs.h:2087 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x760/0x8d0 fs/read_write.c:590
 ksys_write+0xeb/0x1a0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffff8881057f0210 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14117 Comm: syz-executor.0 Not tainted 6.8.0-rc5-syzkaller-00278-g603c04e27c3e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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