[Linux-NTFS-Dev] [syzbot] KASAN: out-of-bounds Read in ntfs_are_names_equal

[syzbot <syz...@sy...>]

Hello,

syzbot found the following issue on:

HEAD commit:    0840a7914caa Merge tag 'char-misc-5.19-rc4' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=137af970080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e771627480f67502
dashboard link: https://syzkaller.appspot.com/bug?extid=d6c974f22abc4a2d3d1c
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=112fd917f00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1201eae4080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syz...@sy...

ntfs: volume version 3.1.
==================================================================
BUG: KASAN: out-of-bounds in ntfs_ucsncmp fs/ntfs/unistr.c:142 [inline]
BUG: KASAN: out-of-bounds in ntfs_are_names_equal+0x196/0x1a0 fs/ntfs/unistr.c:61
Read of size 2 at addr ffff88802a193ee8 by task syz-executor231/3671

CPU: 2 PID: 3671 Comm: syz-executor231 Not tainted 5.19.0-rc3-syzkaller-00336-g0840a7914caa #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0xeb/0x467 mm/kasan/report.c:313
 print_report mm/kasan/report.c:429 [inline]
 kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
 ntfs_ucsncmp fs/ntfs/unistr.c:142 [inline]
 ntfs_are_names_equal+0x196/0x1a0 fs/ntfs/unistr.c:61
 ntfs_attr_find+0x3df/0xb20 fs/ntfs/attrib.c:614
 ntfs_attr_lookup+0x1051/0x2060 fs/ntfs/attrib.c:1189
 ntfs_read_locked_attr_inode fs/ntfs/inode.c:1239 [inline]
 ntfs_attr_iget+0x652/0x26f0 fs/ntfs/inode.c:238
 ntfs_read_locked_inode+0x2494/0x5ae0 fs/ntfs/inode.c:960
 ntfs_iget+0x12d/0x180 fs/ntfs/inode.c:177
 load_system_files fs/ntfs/super.c:1974 [inline]
 ntfs_fill_super+0x5634/0x9080 fs/ntfs/super.c:2891
 mount_bdev+0x34d/0x410 fs/super.c:1367
 legacy_get_tree+0x105/0x220 fs/fs_context.c:610
 vfs_get_tree+0x89/0x2f0 fs/super.c:1497
 do_new_mount fs/namespace.c:3040 [inline]
 path_mount+0x1320/0x1fa0 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f982d4f84aa
Code: 48 c7 c2 c0 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 a8 00 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe6c4048f8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe6c404950 RCX: 00007f982d4f84aa
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffe6c404910
RBP: 00007ffe6c404910 R08: 00007ffe6c404950 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 0000000020001208
R13: 0000000000000003 R14: 0000000000000004 R15: 00000000000000ab
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0000a864c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x2a193
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea000093d4c8 ffffea000093c7c8 0000000000000000
raw: 0000000000000001 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 3672, tgid 3672 (dhcpcd), ts 55153784089, free_ts 55158770564
 prep_new_page mm/page_alloc.c:2456 [inline]
 get_page_from_freelist+0x1290/0x3b70 mm/page_alloc.c:4198
 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5426
 __folio_alloc+0x12/0x40 mm/page_alloc.c:5457
 vma_alloc_folio+0xf9/0x840 mm/mempolicy.c:2233
 alloc_page_vma include/linux/gfp.h:634 [inline]
 wp_page_copy+0x1f6/0x1e20 mm/memory.c:3104
 do_wp_page+0x389/0x1b60 mm/memory.c:3471
 handle_pte_fault mm/memory.c:4921 [inline]
 __handle_mm_fault+0x2371/0x3f50 mm/memory.c:5042
 handle_mm_fault+0x1c8/0x790 mm/memory.c:5140
 do_user_addr_fault+0x489/0x11c0 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1484 [inline]
 exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1540
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:570
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1371 [inline]
 free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1421
 free_unref_page_prepare mm/page_alloc.c:3343 [inline]
 free_unref_page_list+0x16f/0xf80 mm/page_alloc.c:3475
 release_pages+0xff1/0x2290 mm/swap.c:980
 tlb_batch_pages_flush+0xa8/0x1a0 mm/mmu_gather.c:58
 tlb_flush_mmu_free mm/mmu_gather.c:255 [inline]
 tlb_flush_mmu mm/mmu_gather.c:262 [inline]
 tlb_finish_mmu+0x147/0x7e0 mm/mmu_gather.c:353
 exit_mmap+0x1de/0x4a0 mm/mmap.c:3164
 __mmput+0x122/0x4b0 kernel/fork.c:1187
 mmput+0x56/0x60 kernel/fork.c:1208
 exit_mm kernel/exit.c:510 [inline]
 do_exit+0xa12/0x2a00 kernel/exit.c:782
 do_group_exit+0xd2/0x2f0 kernel/exit.c:925
 __do_sys_exit_group kernel/exit.c:936 [inline]
 __se_sys_exit_group kernel/exit.c:934 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:934
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Memory state around the buggy address:
 ffff88802a193d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88802a193e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88802a193e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff88802a193f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88802a193f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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