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+0x67/0xb0 lib/string.c:400
Read of size 1 at addr ffff88805aea48a6 by task syz.4.17/4426

CPU: 1 PID: 4426 Comm: syz.4.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 strcmp+0x67/0xb0 lib/string.c:400
 hpfs_get_ea+0x132/0xdd0 fs/hpfs/ea.c:139
 hpfs_read_inode+0x1a3/0x1050 fs/hpfs/inode.c:63
 hpfs_fill_super+0x135a/0x1fd0 fs/hpfs/super.c:712
 mount_bdev+0x287/0x3c0 fs/super.c:1400
 legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x24a/0xa40 fs/namespace.c:3034
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3562
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f484a41920a
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:00007f4848671e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f4848671ee0 RCX: 00007f484a41920a
RDX: 000020000000a000 RSI: 0000200000009ec0 RDI: 00007f4848671ea0
RBP: 000020000000a000 R08: 00007f4848671ee0 R09: 0000000001200041
R10: 0000000001200041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007f4848671ea0 R14: 0000000000009e15 R15: 0000200000000040
 </TASK>

The buggy address belongs to the page:
page:ffffea00016ba900 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x100 pfn:0x5aea4
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00016baf08 ffffea000178cb08 0000000000000000
raw: 0000000000000100 0000000000000001 00000000ffffff7f 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 0x1100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 4176, ts 63287736075, free_ts 63331839029
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5487
 alloc_pages_vma+0x393/0x7c0 mm/mempolicy.c:2146
 do_anonymous_page mm/memory.c:3838 [inline]
 handle_pte_fault mm/memory.c:4648 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x23be/0x4410 mm/memory.c:4883
 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1355
 handle_page_fault arch/x86/mm/fault.c:1443 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1496
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
 copy_user_enhanced_fast_string+0xe/0x40 arch/x86/lib/copy_user_64.S:205
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 copyout lib/iov_iter.c:157 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:228 [inline]
 __copy_page_to_iter lib/iov_iter.c:861 [inline]
 copy_page_to_iter+0x49e/0x910 lib/iov_iter.c:889
 filemap_read+0x1e2d/0x2540 mm/filemap.c:2698
 blkdev_read_iter+0x11d/0x150 block/fops.c:563
 call_read_iter include/linux/fs.h:2167 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x759/0xd60 fs/read_write.c:485
 ksys_read+0x152/0x260 fs/read_write.c:623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x119/0x820 mm/page_alloc.c:3433
 release_pages+0x186c/0x1be0 mm/swap.c:963
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x176/0x300 mm/mmu_gather.c:338
 unmap_region+0x344/0x3b0 mm/mmap.c:2669
 __do_munmap+0x9f8/0xdf0 mm/mmap.c:2899
 __vm_munmap+0x140/0x240 mm/mmap.c:2952
 __do_sys_munmap mm/mmap.c:2978 [inline]
 __se_sys_munmap mm/mmap.c:2974 [inline]
 __x64_sys_munmap+0x67/0x70 mm/mmap.c:2974
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff88805aea4780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805aea4800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805aea4880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff88805aea4900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805aea4980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================