loop5: rw=8390657, sector=142, nr_sectors = 2 limit=128
Buffer I/O error on dev loop5, logical block 71, lost async page write
syz.5.3404: attempt to access beyond end of device
loop5: rw=8390657, sector=144, nr_sectors = 2 limit=128
Buffer I/O error on dev loop5, logical block 72, lost async page write
syz.5.3404: attempt to access beyond end of device
loop5: rw=2049, sector=146, nr_sectors = 104 limit=128
==================================================================
BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88811d8c2d98 of 8 bytes by interrupt on cpu 1:
 instrument_read_write include/linux/instrumented.h:56 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
 ___test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:114 [inline]
 node_clear_mark lib/xarray.c:102 [inline]
 xas_clear_mark lib/xarray.c:922 [inline]
 __xa_clear_mark+0xf5/0x1e0 lib/xarray.c:2103
 __folio_end_writeback+0xe7/0x530 mm/page-writeback.c:2965
 folio_end_writeback_no_dropbehind+0x6d/0x200 mm/filemap.c:1672
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1698
 mpage_write_end_io+0x245/0x4c0 fs/mpage.c:64
 bio_endio+0x390/0x570 block/bio.c:1929
 blk_update_request+0x33a/0x710 block/blk-mq.c:1016
 blk_mq_end_request+0x26/0x50 block/blk-mq.c:1147
 lo_complete_rq+0x98/0x130 drivers/block/loop.c:315
 blk_complete_reqs block/blk-mq.c:1222 [inline]
 blk_done_softirq+0x77/0xb0 block/blk-mq.c:1227
 handle_softirqs+0xcc/0x2a0 kernel/softirq.c:645
 run_ksoftirqd+0x1c/0x30 kernel/softirq.c:1099
 smpboot_thread_fn+0x32f/0x520 kernel/smpboot.c:160
 kthread+0x223/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88811d8c2d98 of 8 bytes by task 16011 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x211/0x650 lib/xarray.c:1513
 find_get_entry mm/filemap.c:2087 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2353
 __filemap_fdatawait_range mm/filemap.c:523 [inline]
 filemap_fdatawait_range+0x88/0x1e0 mm/filemap.c:558
 filemap_fdatawait include/linux/pagemap.h:51 [inline]
 __writeback_single_inode+0xd9/0x790 fs/fs-writeback.c:1798
 writeback_single_inode+0x16d/0x410 fs/fs-writeback.c:1926
 sync_inode_metadata+0x6e/0xa0 fs/fs-writeback.c:3100
 fat_free fs/fat/file.c:336 [inline]
 fat_truncate_blocks+0x1f1/0x5b0 fs/fat/file.c:397
 fat_write_failed fs/fat/inode.c:219 [inline]
 fat_write_begin+0xc0/0xe0 fs/fat/inode.c:234
 generic_cont_expand_simple+0xb0/0x150 fs/buffer.c:2397
 fat_cont_expand+0x3e/0x170 fs/fat/file.c:226
 fat_fallocate+0x177/0x1c0 fs/fat/file.c:304
 vfs_fallocate+0x3ac/0x400 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0x7a/0xd0 fs/open.c:365
 x64_sys_call+0x1e1d/0x2550 arch/x86/include/generated/asm/syscalls_64.h:286
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000c000 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 16011 Comm: syz.5.3404 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
syz.5.3404: attempt to access beyond end of device
loop5: rw=8390657, sector=140, nr_sectors = 2 limit=128
Buffer I/O error on dev loop5, logical block 70, lost async page write