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 ffff888036020003 by task syz.6.3262/20464

CPU: 1 UID: 0 PID: 20464 Comm: syz.6.3262 Not tainted 6.16.0-rc7-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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/0x230 mm/kasan/report.c:480
 kasan_report+0x118/0x150 mm/kasan/report.c:593
 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+0x12bd/0x2070 fs/hpfs/super.c:654
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1681
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
 do_new_mount+0x24a/0xa40 fs/namespace.c:3902
 do_mount fs/namespace.c:4239 [inline]
 __do_sys_mount fs/namespace.c:4450 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4427
 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: 0033:0x7f732719014a
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:00007f7328014e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f7328014ef0 RCX: 00007f732719014a
RDX: 0000200000009e80 RSI: 0000200000009ec0 RDI: 00007f7328014eb0
RBP: 0000200000009e80 R08: 00007f7328014ef0 R09: 0000000000200041
R10: 0000000000200041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007f7328014eb0 R14: 0000000000009e02 R15: 0000200000009fc0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x433 pfn:0x36020
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 00fff00000000000 ffffea0001273008 ffffea000118ec08 0000000000000000
raw: 0000000000000433 0000000000000004 00000000f0000000 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 20162, tgid 20161 (syz.2.3202), ts 1560020207951, free_ts 1560650211349
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2438
 shmem_alloc_folio mm/shmem.c:1851 [inline]
 shmem_alloc_and_add_folio+0x447/0xf60 mm/shmem.c:1890
 shmem_get_folio_gfp+0x59d/0x1660 mm/shmem.c:2536
 shmem_fault+0x179/0x390 mm/shmem.c:2737
 __do_fault+0x138/0x390 mm/memory.c:5169
 do_read_fault mm/memory.c:5590 [inline]
 do_fault mm/memory.c:5724 [inline]
 do_pte_missing mm/memory.c:4251 [inline]
 handle_pte_fault mm/memory.c:6069 [inline]
 __handle_mm_fault+0x37ed/0x5620 mm/memory.c:6212
 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6381
 faultin_page mm/gup.c:1186 [inline]
 __get_user_pages+0x1af4/0x30b0 mm/gup.c:1488
 populate_vma_page_range+0x26b/0x340 mm/gup.c:1926
 __mm_populate+0x24c/0x380 mm/gup.c:2029
 mm_populate include/linux/mm.h:3353 [inline]
 vm_mmap_pgoff+0x3f0/0x4c0 mm/util.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
page last free pid 20179 tgid 20161 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 free_unref_folios+0xc66/0x14d0 mm/page_alloc.c:2763
 folios_put_refs+0x559/0x640 mm/swap.c:992
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x49e/0x14b0 mm/shmem.c:1125
 shmem_truncate_range mm/shmem.c:1237 [inline]
 shmem_evict_inode+0x272/0xa70 mm/shmem.c:1365
 evict+0x504/0x9c0 fs/inode.c:810
 __dentry_kill+0x209/0x660 fs/dcache.c:669
 dput+0x19f/0x2b0 fs/dcache.c:911
 __fput+0x68e/0xa70 fs/file_table.c:473
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x6b5/0x22e0 kernel/exit.c:964
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1105
 get_signal+0x1286/0x1340 kernel/signal.c:3034
 arch_do_signal_or_restart+0x9a/0x750 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x75/0x110 kernel/entry/common.c:111
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803601ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88803601ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888036020000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888036020080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888036020100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================