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 ffff8881b1ac2b6a by task syz.7.240/7411

CPU: 1 UID: 0 PID: 7411 Comm: syz.7.240 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+0x92/0x2a0
 do_new_mount+0x302/0xa10
 __se_sys_mount+0x313/0x410
 do_syscall_64+0xfa/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6a94190f6a
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:00007f6a950bbe68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f6a950bbef0 RCX: 00007f6a94190f6a
RDX: 0000200000000000 RSI: 0000200000009ec0 RDI: 00007f6a950bbeb0
RBP: 0000200000000000 R08: 00007f6a950bbef0 R09: 0000000003200041
R10: 0000000003200041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007f6a950bbeb0 R14: 0000000000009e2f R15: 0000200000000280
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1ee pfn:0x1b1ac2
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000000000001ee 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 7026, tgid 7025 (syz.2.186), ts 100719153794, free_ts 101547618972
 post_alloc_hook+0x234/0x290
 get_page_from_freelist+0x2365/0x2440
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 folio_alloc_mpol_noprof+0x39/0x70
 shmem_alloc_and_add_folio+0x423/0xf40
 shmem_get_folio_gfp+0x59d/0x1660
 shmem_write_begin+0x16c/0x330
 generic_perform_write+0x2c5/0x900
 shmem_file_write_iter+0xf8/0x120
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5830 tgid 5830 stack trace:
 free_unref_folios+0xdb3/0x14f0
 folios_put_refs+0x584/0x670
 shmem_undo_range+0x49e/0x1490
 shmem_evict_inode+0x26e/0xa70
 evict+0x5f4/0xae0
 __dentry_kill+0x209/0x660
 finish_dput+0xc9/0x480
 __fput+0x68e/0xa70
 task_work_run+0x1d4/0x260
 exit_to_user_mode_loop+0xff/0x4f0
 do_syscall_64+0x2e3/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8881b1ac2a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881b1ac2a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881b1ac2b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                          ^
 ffff8881b1ac2b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881b1ac2c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
