[syzbot] [xfs?] KASAN: use-after-free Read in hpfs_bplus_lookup

[syzbot <syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    b71e635feefc Merge tag 'cgroup-for-6.19-rc5-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10efa99a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7b058fb1d7dbe6b1
dashboard link: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cd15fa580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=152a4052580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/40abbbbc34a8/disk-b71e635f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/74edfb8073f7/vmlinux-b71e635f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3b5198043bfa/bzImage-b71e635f.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/7f1692afbc9c/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1609599a580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/d09b0f5dc58e/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com

hpfs: filesystem error: invalid number of hotfixes: 2066844986, used: 2066844985; already mounted read-only
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: hpfs_map_sector(): read error
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+0x4dc/0x860 fs/hpfs/anode.c:38
Read of size 4 at addr ffff888052abe004 by task syz.0.27/6198

CPU: 1 UID: 0 PID: 6198 Comm: syz.0.27 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 hpfs_bplus_lookup+0x4dc/0x860 fs/hpfs/anode.c:38
 hpfs_bmap+0x22a/0x4d0 fs/hpfs/file.c:54
 hpfs_get_block+0xa8/0x6e0 fs/hpfs/file.c:87
 do_mpage_readpage+0x822/0x1990 fs/mpage.c:222
 mpage_readahead+0x3b0/0x790 fs/mpage.c:371
 read_pages+0x17a/0x580 mm/readahead.c:163
 page_cache_ra_unbounded+0x68b/0x8c0 mm/readahead.c:302
 filemap_get_pages+0x446/0x1ee0 mm/filemap.c:2690
 filemap_read+0x3f9/0x11a0 mm/filemap.c:2800
 __kernel_read+0x4d8/0x970 fs/read_write.c:530
 integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
 ima_calc_file_hash+0x86a/0x1700 security/integrity/ima/ima_crypto.c:568
 ima_collect_measurement+0x42e/0x900 security/integrity/ima/ima_api.c:293
 process_measurement+0x112a/0x1a80 security/integrity/ima/ima_main.c:406
 ima_file_check+0xd9/0x130 security/integrity/ima/ima_main.c:663
 security_file_post_open+0xbb/0x290 security/security.c:2652
 do_open fs/namei.c:4639 [inline]
 path_openat+0x3472/0x3df0 fs/namei.c:4796
 do_filp_open+0x1fa/0x410 fs/namei.c:4823
 do_sys_openat2+0x121/0x200 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb59539f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff3ac53cb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fb5955f5fa0 RCX: 00007fb59539f749
RDX: 0000000000000000 RSI: 0000200000004280 RDI: ffffffffffffff9c
RBP: 00007fb595423f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb5955f5fa0 R14: 00007fb5955f5fa0 R15: 0000000000000004
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb58c615 pfn:0x52abe
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea00014aafc8 ffff8880b8842d30 0000000000000000
raw: 00000007fb58c615 0000000000000000 00000000ffffffff 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 6198, tgid 6198 (syz.0.27), ts 130045840131, free_ts 130049000115
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
 vma_alloc_folio_noprof+0xe4/0x280 mm/mempolicy.c:2540
 folio_prealloc+0x30/0x180 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:5165 [inline]
 do_anonymous_page mm/memory.c:5222 [inline]
 do_pte_missing+0x86a/0x27a0 mm/memory.c:4399
 handle_pte_fault mm/memory.c:6273 [inline]
 __handle_mm_fault mm/memory.c:6411 [inline]
 handle_mm_fault+0xcc1/0x1330 mm/memory.c:6580
 do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
page last free pid 6198 tgid 6198 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
 folios_put_refs+0x569/0x670 mm/swap.c:1002
 free_pages_and_swap_cache+0x4be/0x520 mm/swap_state.c:358
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
 tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
 vms_clear_ptes+0x42b/0x530 mm/vma.c:1238
 vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1280
 do_vmi_align_munmap+0x372/0x450 mm/vma.c:1539
 do_vmi_munmap+0x253/0x2e0 mm/vma.c:1587
 __vm_munmap+0x207/0x380 mm/vma.c:3203
 __do_sys_munmap mm/mmap.c:1077 [inline]
 __se_sys_munmap mm/mmap.c:1074 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1074
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888052abdf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888052abdf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888052abe000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888052abe080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888052abe100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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