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BUG: KCSAN: data-race in fat12_ent_put / fat_parse_short

read to 0xffff8881203713a0 of 11 bytes by task 12109 on cpu 1:
 fat_parse_short+0x15b/0x1190 include/linux/string.h:380
 fat_search_long+0x267/0xc60 fs/fat/dir.c:507
 vfat_find+0xc1/0xd0 fs/fat/namei_vfat.c:698
 vfat_lookup+0x75/0x350 fs/fat/namei_vfat.c:712
 __lookup_slow+0x129/0x2a0 fs/namei.c:1665
 lookup_slow+0x4f/0x70 fs/namei.c:1682
 walk_component+0x490/0xd90 fs/namei.c:1802
 lookup_last fs/namei.c:2260 [inline]
 path_lookupat.isra.0+0x13a/0x5a0 fs/namei.c:2305
 filename_lookup+0x145/0x2b0 fs/namei.c:2335
 user_path_at_empty+0x4c/0x70 fs/namei.c:2615
 user_path_at include/linux/namei.h:49 [inline]
 path_setxattr+0x59/0x150 fs/xattr.c:465
 __do_sys_lsetxattr fs/xattr.c:492 [inline]
 __se_sys_lsetxattr fs/xattr.c:488 [inline]
 __x64_sys_lsetxattr+0x73/0x90 fs/xattr.c:488
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881203713a6 of 1 bytes by task 12100 on cpu 0:
 fat12_ent_put+0xbe/0x1b0 fs/fat/fatent.c:164
 fat_alloc_clusters+0x507/0xc40 fs/fat/fatent.c:501
 fat_add_cluster+0x3d/0xd0 fs/fat/inode.c:107
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x3ae/0x4e0 fs/fat/inode.c:189
 __block_write_begin_int+0x2ea/0xf10 fs/buffer.c:2008
 __block_write_begin fs/buffer.c:2058 [inline]
 block_write_begin+0x77/0x160 fs/buffer.c:2117
 cont_write_begin+0x3d6/0x670 fs/buffer.c:2466
 fat_write_begin+0x72/0xc0 fs/fat/inode.c:235
 generic_perform_write+0x136/0x320 mm/filemap.c:3309
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3438
 generic_file_write_iter+0x28c/0x38c mm/filemap.c:3470
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12100 Comm: syz-executor.1 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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