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+0x6b/0xc0
Read of size 1 at addr ffff8881199fc8a6 by task syz.6.796/9416

CPU: 0 UID: 0 PID: 9416 Comm: syz.6.796 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
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+0xe8/0x150
 print_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 strcmp+0x6b/0xc0
 hpfs_get_ea+0x134/0xee0
 hpfs_read_inode+0x1a6/0x1050
 hpfs_fill_super+0x123d/0x1fa0
 get_tree_bdev_flags+0x431/0x4f0
 vfs_get_tree+0x92/0x2a0
 do_new_mount+0x341/0xd30
 __se_sys_mount+0x31d/0x420
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdf77d9e04a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdf78d36e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fdf78d36ee0 RCX: 00007fdf77d9e04a
RDX: 0000200000000100 RSI: 0000200000000040 RDI: 00007fdf78d36ea0
RBP: 0000200000000100 R08: 00007fdf78d36ee0 R09: 0000000003200041
R10: 0000000003200041 R11: 0000000000000246 R12: 0000200000000040
R13: 00007fdf78d36ea0 R14: 0000000000009e15 R15: 00002000000000c0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x638 pfn:0x1199fc
flags: 0x17ff00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 017ff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000638 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 9346, tgid 9345 (syz.7.780), ts 250270751061, free_ts 253352523998
 post_alloc_hook+0x231/0x280
 get_page_from_freelist+0x24ba/0x2540
 __alloc_frozen_pages_noprof+0x18d/0x380
 alloc_pages_mpol+0x235/0x490
 folio_alloc_mpol_noprof+0x39/0x160
 shmem_alloc_and_add_folio+0x442/0xf80
 shmem_get_folio_gfp+0x5a9/0x1670
 shmem_write_begin+0x16c/0x330
 generic_perform_write+0x2e2/0x8f0
 shmem_file_write_iter+0xf8/0x120
 vfs_write+0x61d/0xb90
 ksys_write+0x150/0x270
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 8745 tgid 8745 stack trace:
 free_unref_folios+0xcec/0x1480
 folios_put_refs+0x9ff/0xb40
 shmem_undo_range+0x52c/0x1660
 shmem_evict_inode+0x289/0xae0
 evict+0x61e/0xb10
 __dentry_kill+0x1a2/0x690
 finish_dput+0xc9/0x480
 __fput+0x691/0xa60
 task_work_run+0x1d9/0x270
 exit_to_user_mode_loop+0xf3/0x4d0
 do_syscall_64+0x33e/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8881199fc780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881199fc800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881199fc880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff8881199fc900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881199fc980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
