syzbot

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hpfs: filesystem error: invalid number of hotfixes: 2066844986, used: 2066844985; already mounted read-only
hpfs: filesystem error: improperly stopped
hpfs: You really don't want any checks? You are crazy...
hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
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BUG: KASAN: use-after-free in strcmp+0x6f/0xb0 lib/string.c:288
Read of size 1 at addr ffff88806bec88a6 by task syz.0.16/5940

CPU: 1 PID: 5940 Comm: syz.0.16 Not tainted 6.6.100-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x200 mm/kasan/report.c:466
 kasan_report+0x117/0x150 mm/kasan/report.c:579
 strcmp+0x6f/0xb0 lib/string.c:288
 hpfs_get_ea+0x115/0xda0 fs/hpfs/ea.c:139
 hpfs_read_inode+0x19e/0x1010 fs/hpfs/inode.c:63
 hpfs_fill_super+0x12d5/0x1ec0 fs/hpfs/super.c:712
 mount_bdev+0x22b/0x2d0 fs/super.c:1643
 legacy_get_tree+0xea/0x180 fs/fs_context.c:662
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3371
 do_mount fs/namespace.c:3711 [inline]
 __do_sys_mount fs/namespace.c:3920 [inline]
 __se_sys_mount+0x2da/0x3c0 fs/namespace.c:3897
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4af719014a
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:00007ffc6e100d38 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc6e100dc0 RCX: 00007f4af719014a
RDX: 0000200000009e80 RSI: 0000200000009ec0 RDI: 00007ffc6e100d80
RBP: 0000200000009e80 R08: 00007ffc6e100dc0 R09: 0000000000000041
R10: 0000000000000041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007ffc6e100d80 R14: 0000000000009e05 R15: 0000200000009f00
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001afb200 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6bec8
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffff7f(buddy)
raw: 00fff00000000000 ffff88813fffa988 ffffea0001afb608 0000000000000000
raw: 0000000000000001 0000000000000003 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5909, tgid 5909 (sed), ts 80232672028, free_ts 80242281790
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 __folio_alloc+0x10/0x20 mm/page_alloc.c:4489
 vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
 do_anonymous_page mm/memory.c:4149 [inline]
 do_pte_missing mm/memory.c:3686 [inline]
 handle_pte_fault mm/memory.c:5025 [inline]
 __handle_mm_fault mm/memory.c:5166 [inline]
 handle_mm_fault+0x1a38/0x4920 mm/memory.c:5331
 do_user_addr_fault+0xad0/0x12e0 arch/x86/mm/fault.c:1324
 handle_page_fault arch/x86/mm/fault.c:1465 [inline]
 exc_page_fault+0x67/0x110 arch/x86/mm/fault.c:1521
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 tlb_batch_pages_flush mm/mmu_gather.c:98 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:293 [inline]
 tlb_flush_mmu+0x368/0x4f0 mm/mmu_gather.c:300
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:392
 exit_mmap+0x3f0/0xb50 mm/mmap.c:3311
 __mmput+0x118/0x3c0 kernel/fork.c:1355
 exit_mm+0x1da/0x2c0 kernel/exit.c:569
 do_exit+0x88e/0x23c0 kernel/exit.c:870
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 __do_sys_exit_group kernel/exit.c:1035 [inline]
 __se_sys_exit_group kernel/exit.c:1033 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88806bec8780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806bec8800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806bec8880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff88806bec8900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806bec8980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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