syzbot

loop2: detected capacity change from 0 to 128
==================================================================
BUG: KCSAN: data-race in xas_find_marked / xas_set_mark

write to 0xffff88811a83da14 of 4 bytes by task 4770 on cpu 1:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark+0x12b/0x140 lib/xarray.c:900
 __folio_start_writeback+0x155/0x390 mm/page-writeback.c:3044
 mpage_write_folio fs/mpage.c:621 [inline]
 mpage_writepages+0xd18/0x1250 fs/mpage.c:670
 fat_writepages+0x24/0x30 fs/fat/inode.c:199
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2604
 filemap_fdatawrite_wbc mm/filemap.c:389 [inline]
 __filemap_fdatawrite_range mm/filemap.c:422 [inline]
 file_write_and_wait_range+0x156/0x2c0 mm/filemap.c:797
 __generic_file_fsync+0x46/0x140 fs/libfs.c:1539
 fat_file_fsync+0x49/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x10d/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3046 [inline]
 generic_file_write_iter+0x1b8/0x2f0 mm/filemap.c:4389
 iter_file_splice_write+0x666/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a83da14 of 4 bytes by task 4767 on cpu 0:
 xa_marked include/linux/xarray.h:424 [inline]
 xas_find_marked+0x5dc/0x620 lib/xarray.c:1483
 find_get_entry+0x5d/0x380 mm/filemap.c:2070
 filemap_get_folios_tag+0x92/0x210 mm/filemap.c:2338
 __filemap_fdatawait_range mm/filemap.c:533 [inline]
 filemap_fdatawait_range+0x88/0x1d0 mm/filemap.c:568
 filemap_fdatawait include/linux/pagemap.h:50 [inline]
 __writeback_single_inode+0xdb/0x7c0 fs/fs-writeback.c:1729
 writeback_single_inode+0x16d/0x3f0 fs/fs-writeback.c:1840
 sync_inode_metadata+0x5b/0x90 fs/fs-writeback.c:2923
 __generic_file_fsync+0xf8/0x140 fs/libfs.c:1550
 fat_file_fsync+0x49/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x10d/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3046 [inline]
 generic_file_write_iter+0x1b8/0x2f0 mm/filemap.c:4389
 iter_file_splice_write+0x666/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0a000021 -> 0x04000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4767 Comm: syz.2.463 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================
syz.2.463: attempt to access beyond end of device
loop2: rw=2049, sector=128, nr_sectors = 1 limit=128
Buffer I/O error on dev loop2, logical block 128, lost async page write
syz.2.463 (4767) used greatest stack depth: 10072 bytes left