==================================================================
BUG: KCSAN: data-race in _copy_to_iter / fat12_ent_put

read-write to 0xffff88813b578291 of 1 bytes by task 3258 on cpu 1:
 fat12_ent_put+0xc6/0x180 fs/fat/fatent.c:165
 fat_ent_write+0x5e/0xd0 fs/fat/fatent.c:417
 fat_chain_add+0x15b/0x410 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+0x486/0x600 fs/fat/inode.c:190
 __block_write_begin_int+0x30d/0xbc0 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x73/0x170 fs/buffer.c:2117
 cont_write_begin+0x3f1/0x520 fs/buffer.c:2471
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 cont_expand_zero fs/buffer.c:2398 [inline]
 cont_write_begin+0x1a0/0x520 fs/buffer.c:2461
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 generic_cont_expand_simple+0xa9/0x140 fs/buffer.c:2362
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_setattr+0x356/0x9b0 fs/fat/file.c:512
 notify_change+0x9f8/0xb20 fs/attr.c:420
 do_truncate fs/open.c:65 [inline]
 do_sys_ftruncate+0x317/0x420 fs/open.c:193
 __do_sys_ftruncate fs/open.c:204 [inline]
 __se_sys_ftruncate fs/open.c:202 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:202
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813b578000 of 1024 bytes by task 2979 on cpu 0:
 instrument_copy_to_user include/linux/instrumented.h:119 [inline]
 copyout lib/iov_iter.c:169 [inline]
 _copy_to_iter+0x11d/0x8b0 lib/iov_iter.c:524
 copy_page_to_iter+0x333/0x3f0 lib/iov_iter.c:722
 copy_folio_to_iter include/linux/uio.h:169 [inline]
 filemap_read+0x119b/0x1430 mm/filemap.c:2711
 blkdev_read_iter+0x2c6/0x370 block/fops.c:598
 call_read_iter include/linux/fs.h:2186 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3a5/0x560 fs/read_write.c:470
 ksys_read+0xe8/0x1a0 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2979 Comm: udevd Not tainted 5.19.0-syzkaller-13930-g7ebfc85e2cd7-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
==================================================================
I/O error, dev loop4, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
Buffer I/O error on dev loop4, logical block 0, async page read
I/O error, dev loop4, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
Buffer I/O error on dev loop4, logical block 0, async page read