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BUG: KCSAN: data-race in mark_buffer_dirty_inode / sync_mapping_buffers

write to 0xffff888106991538 of 8 bytes by task 3493 on cpu 1:
 __remove_assoc_queue fs/buffer.c:514 [inline]
 fsync_buffers_list fs/buffer.c:785 [inline]
 sync_mapping_buffers+0x159/0x7c0 fs/buffer.c:575
 fat_file_fsync+0xa7/0x100 fs/fat/file.c:195
 vfs_fsync_range+0x116/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:2958 [inline]
 generic_file_write_iter+0x1c3/0x310 mm/filemap.c:4320
 iter_file_splice_write+0x5f1/0x980 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x160/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x302/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x398/0x660 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1424 [inline]
 __se_sys_sendfile64 fs/read_write.c:1410 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1410
 x64_sys_call+0xfbd/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888106991538 of 8 bytes by task 3483 on cpu 0:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:678
 fat16_ent_put+0x4f/0x60 fs/fat/fatent.c:184
 fat_ent_write+0x66/0xe0 fs/fat/fatent.c:417
 fat_chain_add+0x15f/0x400 fs/fat/misc.c:136
 fat_add_cluster fs/fat/inode.c:112 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x46b/0x5e0 fs/fat/inode.c:189
 __block_write_begin_int+0x417/0xfa0 fs/buffer.c:2116
 block_write_begin fs/buffer.c:2226 [inline]
 cont_write_begin+0x546/0x860 fs/buffer.c:2577
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 cont_expand_zero fs/buffer.c:2504 [inline]
 cont_write_begin+0x18b/0x860 fs/buffer.c:2567
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 generic_cont_expand_simple+0xaa/0x150 fs/buffer.c:2468
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_fallocate+0x17c/0x1d0 fs/fat/file.c:301
 vfs_fallocate+0x368/0x3b0 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0x78/0xc0 fs/open.c:365
 x64_sys_call+0x43c/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:286
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888116185108 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3483 Comm: syz.2.13 Not tainted 6.13.0-syzkaller-09030-g6d61a53dd6f5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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