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BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff888106c92b50 of 8 bytes by task 6119 on cpu 0:
 mark_buffer_dirty_inode+0x18d/0x1c0 fs/buffer.c:682
 fat_mirror_bhs+0x241/0x330 fs/fat/fatent.c:398
 fat_alloc_clusters+0x994/0xa80 fs/fat/fatent.c:543
 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:2125
 __block_write_begin fs/buffer.c:2174 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2235
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2587
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:229
 generic_perform_write+0x1b4/0x580 mm/filemap.c:4019
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4121
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4147
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x78f/0x900 fs/read_write.c:590
 ksys_write+0xeb/0x1b0 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
 x64_sys_call+0x27dd/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:2
 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 0xffff888106c92b50 of 8 bytes by task 6122 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:678
 fat_mirror_bhs+0x241/0x330 fs/fat/fatent.c:398
 fat_ent_write+0xcc/0xe0 fs/fat/fatent.c:423
 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:2125
 __block_write_begin fs/buffer.c:2174 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2235
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2587
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:229
 generic_perform_write+0x1b4/0x580 mm/filemap.c:4019
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4121
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4147
 __kernel_write_iter+0x24f/0x4e0 fs/read_write.c:523
 __kernel_write+0x90/0xc0 fs/read_write.c:543
 __dump_emit fs/coredump.c:816 [inline]
 dump_emit+0x1a8/0x270 fs/coredump.c:853
 elf_core_dump+0x16fb/0x1c30 fs/binfmt_elf.c:2095
 do_coredump+0xfa7/0x1810 fs/coredump.c:767
 get_signal+0xdc1/0x1080 kernel/signal.c:2902
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 irqentry_exit_to_user_mode+0x9a/0x130 kernel/entry/common.c:231
 irqentry_exit+0x12/0x50 kernel/entry/common.c:334
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

value changed: 0x0000000000000000 -> 0xffff8881171e2c08

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6122 Comm: syz.4.603 Not tainted 6.11.0-rc4-syzkaller-00008-g6e4436539ae1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
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syz.4.603 (6122) used greatest stack depth: 9768 bytes left