Re: [syzbot] [ntfs3?] KASAN: slab-out-of-bounds Read in ntfs_utf16_to_nls

[syzbot <syzbot+598057afa0f49e62bd23@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-out-of-bounds Read in ntfs_utf16_to_nls

nl: 254, name: file0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, ntfs_dir_emit
keysize: 76, name len: 255, nls: ffffffff8e445280, fn: f, ntfs_dir_emit
ntfs3(loop0): failed to convert "0000" to maccroatian
==================================================================
BUG: KASAN: slab-out-of-bounds in ntfs_utf16_to_nls+0x3c9/0x5a0 fs/ntfs3/dir.c:49
Read of size 2 at addr ffff888033905000 by task syz.0.16/6595

CPU: 1 UID: 0 PID: 6595 Comm: syz.0.16 Not tainted 6.15.0-syzkaller-12141-gec7714e49479-dirty #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:408 [inline]
 print_report+0xd2/0x2b0 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 ntfs_utf16_to_nls+0x3c9/0x5a0 fs/ntfs3/dir.c:49
 ntfs_dir_emit fs/ntfs3/dir.c:310 [inline]
 ntfs_read_hdr+0x6b5/0xca0 fs/ntfs3/dir.c:387
 ntfs_readdir+0xa5c/0xdd0 fs/ntfs3/dir.c:498
 iterate_dir+0x5ac/0x770 fs/readdir.c:108
 __do_sys_getdents64 fs/readdir.c:410 [inline]
 __se_sys_getdents64+0xe4/0x260 fs/readdir.c:396
 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: 0033:0x7f414938e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007f414a2cd038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f41495b5fa0 RCX: 00007f414938e969
RDX: 0000000000001000 RSI: 0000200000000f80 RDI: 0000000000000004
RBP: 00007f4149410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f41495b5fa0 R15: 00007fffafbf4148
 </TASK>

Allocated by task 6595:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4328 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 indx_read+0x27c/0xc20 fs/ntfs3/index.c:1059
 ntfs_readdir+0x9d8/0xdd0 fs/ntfs3/dir.c:493
 iterate_dir+0x5ac/0x770 fs/readdir.c:108
 __do_sys_getdents64 fs/readdir.c:410 [inline]
 __se_sys_getdents64+0xe4/0x260 fs/readdir.c:396
 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

The buggy address belongs to the object at ffff888033904000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 0 bytes to the right of
 allocated 4096-byte region [ffff888033904000, ffff888033905000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x33900
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a442140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a442140 dead000000000122 0000000000000000
head: 0000000000000000 0000000080040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000ce4001 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6595, tgid 6594 (syz.0.16), ts 131229531839, free_ts 131158758528
 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+0x21d5/0x22b0 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
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2619
 new_slab mm/slub.c:2673 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
 __slab_alloc mm/slub.c:3949 [inline]
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x305/0x4f0 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 indx_read+0x27c/0xc20 fs/ntfs3/index.c:1059
 indx_find+0x4bb/0xba0 fs/ntfs3/index.c:1179
 indx_insert_entry+0x4f1/0x720 fs/ntfs3/index.c:1963
 ntfs_create_inode+0x2317/0x3340 fs/ntfs3/inode.c:1620
 ntfs_mknod+0x3b/0x50 fs/ntfs3/namei.c:120
 vfs_mknod+0x37f/0x3c0 fs/namei.c:4235
 do_mknodat+0x385/0x4d0 fs/namei.c:-1
 __do_sys_mknod fs/namei.c:4318 [inline]
 __se_sys_mknod fs/namei.c:4316 [inline]
 __x64_sys_mknod+0x8c/0xa0 fs/namei.c:4316
 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 6275 tgid 6275 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0xc65/0xe60 mm/page_alloc.c:2706
 discard_slab mm/slub.c:2717 [inline]
 __put_partials+0x161/0x1c0 mm/slub.c:3186
 put_cpu_partial+0x17c/0x250 mm/slub.c:3261
 __slab_free+0x2f7/0x400 mm/slub.c:4513
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4148 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4204
 anon_vma_chain_alloc mm/rmap.c:142 [inline]
 __anon_vma_prepare+0xcb/0x4a0 mm/rmap.c:195
 __vmf_anon_prepare mm/memory.c:3523 [inline]
 vmf_anon_prepare mm/internal.h:410 [inline]
 do_anonymous_page mm/memory.c:5087 [inline]
 do_pte_missing mm/memory.c:4249 [inline]
 handle_pte_fault mm/memory.c:6089 [inline]
 __handle_mm_fault+0x4d02/0x5620 mm/memory.c:6232
 handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6401
 do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1387
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

Memory state around the buggy address:
 ffff888033904f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888033904f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888033905000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888033905080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888033905100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         ec7714e4 Merge tag 'rust-6.16' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=136f31d4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=26abb92f9ef9d1d0
dashboard link: https://syzkaller.appspot.com/bug?extid=598057afa0f49e62bd23
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1411e570580000