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
Read of size 1 at addr ffff888042c968a6 by task syz.4.208/7226

CPU: 0 UID: 0 PID: 7226 Comm: syz.4.208 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 strcmp+0x6f/0xc0
 hpfs_get_ea+0x114/0xdb0
 hpfs_read_inode+0x19d/0x1010
 hpfs_fill_super+0x129d/0x2040
 get_tree_bdev_flags+0x40e/0x4d0
 vfs_get_tree+0x92/0x2b0
 do_new_mount+0x2ee/0xa90
 __se_sys_mount+0x317/0x410
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f440c39038a
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:00007f440d218e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f440d218ef0 RCX: 00007f440c39038a
RDX: 000020000000a000 RSI: 0000200000009ec0 RDI: 00007f440d218eb0
RBP: 000020000000a000 R08: 00007f440d218ef0 R09: 0000000003a00041
R10: 0000000003a00041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007f440d218eb0 R14: 0000000000009e22 R15: 00002000000001c0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xfda pfn:0x42c96
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00010b25c8 ffffea00010b1d88 0000000000000000
raw: 0000000000000fda 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 7196, tgid 7195 (syz.4.204), ts 126556053093, free_ts 127387094552
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 folio_alloc_mpol_noprof+0x39/0x70
 shmem_alloc_and_add_folio+0x447/0xf60
 shmem_get_folio_gfp+0x59d/0x1660
 shmem_write_begin+0xf7/0x2b0
 generic_perform_write+0x2c5/0x900
 shmem_file_write_iter+0xf8/0x120
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 6928 tgid 6928 stack trace:
 free_unref_folios+0xdb3/0x14f0
 folios_put_refs+0x584/0x670
 shmem_undo_range+0x49e/0x14b0
 shmem_evict_inode+0x272/0xa70
 evict+0x504/0x9c0
 __dentry_kill+0x209/0x660
 dput+0x19f/0x2b0
 __fput+0x68e/0xa70
 task_work_run+0x1d4/0x260
 exit_to_user_mode_loop+0xec/0x130
 do_syscall_64+0x2bd/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888042c96780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888042c96800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888042c96880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff888042c96900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888042c96980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
