hpfs: You really don't want any checks? You are crazy...
hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================
BUG: KASAN: use-after-free in strcmp+0x6f/0xc0 lib/string.c:283
Read of size 1 at addr ffff888084d708a6 by task syz.0.3404/19641

CPU: 0 UID: 0 PID: 19641 Comm: syz.0.3404 Not tainted 6.17.0-rc1-next-20250814-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 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
 strcmp+0x6f/0xc0 lib/string.c:283
 hpfs_get_ea+0x114/0xdb0 fs/hpfs/ea.c:139
 hpfs_read_inode+0x19d/0x1010 fs/hpfs/inode.c:63
 hpfs_fill_super+0x129d/0x2040 fs/hpfs/super.c:654
 get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1692
 vfs_get_tree+0x8f/0x2b0 fs/super.c:1752
 do_new_mount+0x2a2/0xa30 fs/namespace.c:3807
 do_mount fs/namespace.c:4135 [inline]
 __do_sys_mount fs/namespace.c:4346 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4323
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7febbfd9038a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007febc0b30e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007febc0b30ef0 RCX: 00007febbfd9038a
RDX: 0000200000009e80 RSI: 0000200000009ec0 RDI: 00007febc0b30eb0
RBP: 0000200000009e80 R08: 00007febc0b30ef0 R09: 0000000000200041
R10: 0000000000200041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007febc0b30eb0 R14: 0000000000009e02 R15: 0000200000009fc0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x2776 pfn:0x84d70
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea000251d3c8 ffffea0002135c48 0000000000000000
raw: 0000000000002776 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 19591, tgid 19590 (syz.1.3398), ts 1045646126239, free_ts 1046416541654
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2435
 shmem_alloc_folio mm/shmem.c:1908 [inline]
 shmem_alloc_and_add_folio+0x447/0xf60 mm/shmem.c:1947
 shmem_get_folio_gfp+0x59d/0x1660 mm/shmem.c:2597
 shmem_get_folio mm/shmem.c:2703 [inline]
 shmem_fallocate+0x80f/0xde0 mm/shmem.c:3811
 vfs_fallocate+0x666/0x7e0 fs/open.c:342
 ksys_fallocate fs/open.c:366 [inline]
 __do_sys_fallocate fs/open.c:371 [inline]
 __se_sys_fallocate fs/open.c:369 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:369
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 19591 tgid 19590 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 free_unref_folios+0xdbd/0x1520 mm/page_alloc.c:2952
 folios_put_refs+0x559/0x640 mm/swap.c:997
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x49e/0x14b0 mm/shmem.c:1157
 shmem_fallocate+0xc70/0xde0 mm/shmem.c:3817
 vfs_fallocate+0x666/0x7e0 fs/open.c:342
 ksys_fallocate fs/open.c:366 [inline]
 __do_sys_fallocate fs/open.c:371 [inline]
 __se_sys_fallocate fs/open.c:369 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:369
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888084d70780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888084d70800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888084d70880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff888084d70900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888084d70980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================