syzbot

hpfs: filesystem error: improperly stopped
hpfs: filesystem error: warning: spare dnodes used, try chkdsk
hpfs: You really don't want any checks? You are crazy...
hpfs: Code page index out of array
hpfs: code page support is disabled
hpfs: filesystem error: map_dirent: not a directory
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: filesystem error: unable to find root dir
==================================================================
BUG: KASAN: use-after-free in hpfs_bplus_lookup+0x4f4/0x880 fs/hpfs/anode.c:38
Read of size 4 at addr ffff88804b056008 by task syz.0.18/5968

CPU: 1 UID: 0 PID: 5968 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 hpfs_bplus_lookup+0x4f4/0x880 fs/hpfs/anode.c:38
 hpfs_bmap+0x230/0x4e0 fs/hpfs/file.c:54
 hpfs_get_block+0xa8/0x6e0 fs/hpfs/file.c:87
 do_mpage_readpage+0x801/0x1980 fs/mpage.c:221
 mpage_readahead+0x407/0x830 fs/mpage.c:370
 read_pages+0x193/0x5a0 mm/readahead.c:163
 page_cache_ra_unbounded+0x706/0x980 mm/readahead.c:304
 do_page_cache_ra mm/readahead.c:334 [inline]
 page_cache_ra_order+0x2b5/0x490 mm/readahead.c:538
 filemap_get_pages+0x47c/0x1e70 mm/filemap.c:2696
 filemap_read+0x44a/0x1240 mm/filemap.c:2806
 __kernel_read+0x50d/0x9c0 fs/read_write.c:532
 integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
 ima_calc_file_hash+0x452/0x870 security/integrity/ima/ima_crypto.c:280
 ima_collect_measurement+0x523/0x9d0 security/integrity/ima/ima_api.c:300
 process_measurement+0x12d9/0x1c90 security/integrity/ima/ima_main.c:425
 ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
 security_file_post_open+0xb3/0x260 security/security.c:2755
 do_open fs/namei.c:4701 [inline]
 path_openat+0x2e88/0x38a0 fs/namei.c:4858
 do_file_open+0x23e/0x4a0 fs/namei.c:4887
 do_sys_openat2+0x113/0x200 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_open fs/open.c:1378 [inline]
 __se_sys_open fs/open.c:1374 [inline]
 __x64_sys_open+0x11e/0x150 fs/open.c:1374
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0ccd38ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc7f5a03a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f0ccd605fa0 RCX: 00007f0ccd38ce59
RDX: 0000000000000002 RSI: 0000000000080540 RDI: 0000200000000080
RBP: 00007f0ccd422d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0ccd605fac R14: 00007f0ccd605fa0 R15: 00007f0ccd605fa0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xec pfn:0x4b056
flags: 0x80000000000000(node=0|zone=1)
page_type: f0(buddy)
raw: 0080000000000000 ffffea00012d9f88 ffffea00012cb508 0000000000000000
raw: 00000000000000ec 0000000000000001 00000000f0000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x152c4a(GFP_NOFS|__GFP_HIGHMEM|__GFP_MOVABLE|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 5954, tgid 5954 (syz.0.17), ts 119924664404, free_ts 122607774413
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x28b2/0x2930 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2490
 alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
 alloc_pages_noprof+0xd2/0x2f0 mm/mempolicy.c:2581
 folio_alloc_noprof+0x22/0xc0 mm/mempolicy.c:2591
 filemap_alloc_folio_noprof+0x111/0x4d0 mm/filemap.c:1014
 ractl_alloc_folio mm/readahead.c:189 [inline]
 page_cache_ra_unbounded+0x2f7/0x980 mm/readahead.c:277
 do_page_cache_ra mm/readahead.c:334 [inline]
 page_cache_ra_order+0x2b5/0x490 mm/readahead.c:538
 filemap_readahead mm/filemap.c:2664 [inline]
 filemap_get_pages+0x832/0x1e70 mm/filemap.c:2710
 filemap_read+0x44a/0x1240 mm/filemap.c:2806
 __kernel_read+0x50d/0x9c0 fs/read_write.c:532
 integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
 ima_calc_file_hash+0x452/0x870 security/integrity/ima/ima_crypto.c:280
 ima_collect_measurement+0x523/0x9d0 security/integrity/ima/ima_api.c:300
 process_measurement+0x12d9/0x1c90 security/integrity/ima/ima_main.c:425
page last free pid 5813 tgid 5813 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 free_unref_folios+0xd8d/0x1990 mm/page_alloc.c:2999
 folios_put_refs+0x7cb/0x8d0 mm/swap.c:1008
 folio_batch_release include/linux/folio_batch.h:101 [inline]
 truncate_inode_pages_range+0x3e0/0xe30 mm/truncate.c:408
 hpfs_evict_inode+0x2c/0x150 fs/hpfs/inode.c:311
 evict+0x61e/0xb10 fs/inode.c:841
 dispose_list fs/inode.c:883 [inline]
 evict_inodes+0x75a/0x7f0 fs/inode.c:937
 generic_shutdown_super+0xaa/0x2d0 fs/super.c:632
 kill_block_super+0x44/0x90 fs/super.c:1725
 deactivate_locked_super+0xbc/0x130 fs/super.c:476
 cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0x193/0x680 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88804b055f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88804b055f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88804b056000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88804b056080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804b056100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================