Buffer I/O error on dev loop0, logical block 83, lost async page write
syz.0.2670: attempt to access beyond end of device
loop0: rw=8390657, sector=168, nr_sectors = 2 limit=128
Buffer I/O error on dev loop0, logical block 84, lost async page write
syz.0.2670: attempt to access beyond end of device
loop0: rw=2049, sector=186, nr_sectors = 6 limit=128
==================================================================
BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff88811b2f1d88 of 8 bytes by task 13854 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+0x91/0x180 lib/xarray.c:922
 __folio_start_writeback+0x23e/0x350 mm/page-writeback.c:3032
 __block_write_full_folio+0x526/0x8d0 fs/buffer.c:1905
 block_write_full_folio+0x2c1/0x2e0 fs/buffer.c:-1
 blkdev_writepages+0x88/0x100 block/fops.c:485
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 filemap_write_and_wait_range+0x166/0x370 mm/filemap.c:684
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev+0x35/0x50 block/bdev.c:276
 sync_filesystem+0x162/0x190 fs/sync.c:70
 __do_sys_syncfs fs/sync.c:159 [inline]
 __se_sys_syncfs+0x5e/0xe0 fs/sync.c:148
 __x64_sys_syncfs+0x1f/0x30 fs/sync.c:148
 x64_sys_call+0x9fb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:307
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b2f1d88 of 8 bytes by task 13845 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x211/0x650 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2081 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2348
 writeback_get_folio mm/page-writeback.c:2428 [inline]
 writeback_iter+0x48f/0x7c0 mm/page-writeback.c:2529
 blkdev_writepages+0x69/0x100 block/fops.c:484
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_flush_range mm/filemap.c:436 [inline]
 filemap_flush+0xee/0x130 mm/filemap.c:451
 sync_blockdev_nowait+0x29/0x40 block/bdev.c:264
 fat_flush_inodes+0x131/0x150 fs/fat/inode.c:1910
 fat_truncate_blocks+0x536/0x5b0 fs/fat/file.c:399
 fat_write_failed fs/fat/inode.c:219 [inline]
 fat_write_end+0xba/0x160 fs/fat/inode.c:247
 generic_perform_write+0x314/0x490 mm/filemap.c:4379
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4475
 generic_file_write_iter+0x77/0x1f0 mm/filemap.c:4501
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57d/0x990 fs/read_write.c:687
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000001 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 13845 Comm: syz.0.2670 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
==================================================================
syz.0.2670: attempt to access beyond end of device
loop0: rw=8390657, sector=190, nr_sectors = 2 limit=128
Buffer I/O error on dev loop0, logical block 95, lost async page write
syz.0.2670: attempt to access beyond end of device
loop0: rw=8390657, sector=192, nr_sectors = 2 limit=128
Buffer I/O error on dev loop0, logical block 96, lost async page write