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BUG: KCSAN: data-race in mark_buffer_dirty_inode / sync_mapping_buffers

write to 0xffff8881071da670 of 8 bytes by task 9586 on cpu 0:
 __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:2970 [inline]
 generic_file_write_iter+0x1c3/0x310 mm/filemap.c:4320
 do_iter_readv_writev+0x403/0x4b0
 vfs_writev+0x2d9/0x880 fs/read_write.c:1050
 do_pwritev fs/read_write.c:1146 [inline]
 __do_sys_pwritev2 fs/read_write.c:1204 [inline]
 __se_sys_pwritev2+0x100/0x1c0 fs/read_write.c:1195
 __x64_sys_pwritev2+0x78/0x90 fs/read_write.c:1195
 x64_sys_call+0x2afe/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:329
 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 0xffff8881071da670 of 8 bytes by task 9559 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:678
 fat16_ent_put+0x4f/0x60 fs/fat/fatent.c:184
 fat_alloc_clusters+0x4c9/0xa80 fs/fat/fatent.c:503
 fat_add_cluster fs/fat/inode.c:107 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x25c/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_setattr+0x2aa/0x840 fs/fat/file.c:513
 notify_change+0x85c/0x8e0 fs/attr.c:552
 do_truncate fs/open.c:65 [inline]
 do_ftruncate+0x332/0x440 fs/open.c:192
 do_sys_ftruncate fs/open.c:207 [inline]
 __do_sys_ftruncate fs/open.c:212 [inline]
 __se_sys_ftruncate fs/open.c:210 [inline]
 __x64_sys_ftruncate+0x67/0xc0 fs/open.c:210
 x64_sys_call+0x9d9/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:78
 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: 0xffff888105fe1708 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9559 Comm: syz.6.2196 Not tainted 6.14.0-rc4-syzkaller-00169-g1e15510b71c9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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