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/0xb0 lib/string.c:288
Read of size 1 at addr ffff8880558e88a6 by task syz.1.18/5976

CPU: 1 PID: 5976 Comm: syz.1.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x220 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 strcmp+0x6f/0xb0 lib/string.c:288
 hpfs_get_ea+0x115/0xda0 fs/hpfs/ea.c:139
 hpfs_read_inode+0x19e/0x1010 fs/hpfs/inode.c:63
 hpfs_fill_super+0x12d5/0x1ec0 fs/hpfs/super.c:712
 mount_bdev+0x22b/0x2d0 fs/super.c:1643
 legacy_get_tree+0xea/0x180 fs/fs_context.c:662
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3377
 do_mount fs/namespace.c:3717 [inline]
 __do_sys_mount fs/namespace.c:3926 [inline]
 __se_sys_mount+0x2da/0x3c0 fs/namespace.c:3903
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe35a39034a
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:00007fe3585d4e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fe3585d4ef0 RCX: 00007fe35a39034a
RDX: 000020000000a000 RSI: 0000200000000000 RDI: 00007fe3585d4eb0
RBP: 000020000000a000 R08: 00007fe3585d4ef0 R09: 0000000003200041
R10: 0000000003200041 R11: 0000000000000246 R12: 0000200000000000
R13: 00007fe3585d4eb0 R14: 0000000000009e15 R15: 0000200000000040
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001563a00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x558e8
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0001563a48 ffffea00015639c8 0000000000000000
raw: 0000000000000001 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 5977, tgid 5965 (syz.3.20), ts 107071006728, free_ts 107433449848
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 __folio_alloc+0x10/0x20 mm/page_alloc.c:4489
 vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
 mfill_atomic_pte_copy+0x8e/0x430 mm/userfaultfd.c:153
 mfill_atomic_pte mm/userfaultfd.c:587 [inline]
 mfill_atomic mm/userfaultfd.c:727 [inline]
 mfill_atomic_copy+0x75f/0x1690 mm/userfaultfd.c:778
 userfaultfd_copy fs/userfaultfd.c:1782 [inline]
 userfaultfd_ioctl+0x1dbc/0x4f10 fs/userfaultfd.c:2119
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 shrink_folio_list+0x6fe5/0x7980 mm/vmscan.c:2194
 reclaim_folio_list+0xe4/0x380 mm/vmscan.c:2788
 reclaim_pages+0x564/0x680 mm/vmscan.c:2824
 madvise_cold_or_pageout_pte_range+0x1998/0x2050 mm/madvise.c:533
 walk_pmd_range mm/pagewalk.c:143 [inline]
 walk_pud_range mm/pagewalk.c:221 [inline]
 walk_p4d_range mm/pagewalk.c:256 [inline]
 walk_pgd_range+0xc4c/0x1820 mm/pagewalk.c:293
 __walk_page_range+0x134/0x5b0 mm/pagewalk.c:395
 walk_page_range+0x345/0x510 mm/pagewalk.c:521
 madvise_pageout_page_range mm/madvise.c:592 [inline]
 madvise_pageout mm/madvise.c:619 [inline]
 madvise_vma_behavior mm/madvise.c:1037 [inline]
 madvise_walk_vmas mm/madvise.c:1266 [inline]
 do_madvise+0x23cf/0x3710 mm/madvise.c:1446
 __do_sys_madvise mm/madvise.c:1459 [inline]
 __se_sys_madvise mm/madvise.c:1457 [inline]
 __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:1457
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff8880558e8780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880558e8800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880558e8880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff8880558e8900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880558e8980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================