==================================================================
BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff88814270e5a0 of 8 bytes by task 22489 on cpu 0:
 mark_buffer_dirty_inode+0x190/0x1c0 fs/buffer.c:685
 fat_mirror_bhs+0x247/0x340 fs/fat/fatent.c:398
 fat_alloc_clusters+0x973/0xa60 fs/fat/fatent.c:543
 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+0x3b7/0xf40 fs/buffer.c:2119
 __block_write_begin fs/buffer.c:2168 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2227
 cont_write_begin+0x479/0x690 fs/buffer.c:2582
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1c9/0x410 mm/filemap.c:3918
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4013
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4039
 do_iter_write+0x4ad/0x770 fs/read_write.c:860
 vfs_iter_write+0x56/0x70 fs/read_write.c:901
 iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
 splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
 do_splice_direct+0x10d/0x190 fs/splice.c:1194
 do_sendfile+0x3c4/0x980 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1316 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88814270e5a0 of 8 bytes by task 22490 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:681
 fat_mirror_bhs+0x247/0x340 fs/fat/fatent.c:398
 fat_ent_write+0xc6/0xe0 fs/fat/fatent.c:423
 fat_chain_add+0x15f/0x400 fs/fat/misc.c:136
 fat_add_cluster fs/fat/inode.c:113 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x467/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x3b7/0xf40 fs/buffer.c:2119
 __block_write_begin fs/buffer.c:2168 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2227
 cont_write_begin+0x479/0x690 fs/buffer.c:2582
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 cont_expand_zero fs/buffer.c:2509 [inline]
 cont_write_begin+0x182/0x690 fs/buffer.c:2572
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1c9/0x410 mm/filemap.c:3918
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4013
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4039
 __kernel_write_iter+0x162/0x390 fs/read_write.c:517
 dump_emit_page fs/coredump.c:888 [inline]
 dump_user_range+0x25d/0x480 fs/coredump.c:915
 elf_core_dump+0x1a85/0x1ba0 fs/binfmt_elf.c:2077
 do_coredump+0x102a/0x1890 fs/coredump.c:764
 get_signal+0xdb5/0x10a0 kernel/signal.c:2890
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 irqentry_exit_to_user_mode+0x9/0x20 kernel/entry/common.c:309
 irqentry_exit+0x12/0x40 kernel/entry/common.c:412
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

value changed: 0x0000000000000000 -> 0xffff888106bb5d58

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22490 Comm: syz-executor.5 Not tainted 6.7.0-rc1-syzkaller-00344-g037266a5f723 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================
syz-executor.5 (22490) used greatest stack depth: 9448 bytes left