[syzbot] KASAN: slab-use-after-free Read in ntfs_show_options

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0d8395707651 Merge tag 'soc-fixes-7.2-2' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1783bcc6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a
dashboard link: https://syzkaller.appspot.com/bug?extid=4c22f022eb39c86b9d19
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f877b9580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c22f0...@syzkaller.appspotmail.com

==================================================================
==================================================================
BUG: KASAN: slab-use-after-free in ntfs_show_options+0x656/0x800 fs/ntfs3/super.c:762
Read of size 2 at addr ffff888030028d1c by task syz-executor377/6018

CPU: 0 UID: 0 PID: 6018 Comm: syz-executor377 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ntfs_show_options+0x656/0x800 fs/ntfs3/super.c:762
show_vfsmnt+0x637/0x780 fs/proc_namespace.c:129
seq_read_iter+0x8d6/0xcb0 fs/seq_file.c:273
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x59e/0xa90 fs/read_write.c:574
ksys_read+0x156/0x270 fs/read_write.c:716
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f12f25c661e
Code: 08 0f 85 f5 e2 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
RSP: 002b:00007f12ef560198 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f12ef5616c0 RCX: 00007f12f25c661e
RDX: 0000000000001000 RSI: 00007f12ef560200 RDI: 0000000000000005
RBP: 00007f12f260b03e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f12ef560200
R13: 0000000000000000 R14: 00007fff2ed6d880 R15: 00007fff2ed6d968
</TASK>

Allocated by task 6027:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x3d2/0x6b0 mm/slub.c:5489
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
ntfs_init_fs_context+0x55/0x570 fs/ntfs3/super.c:1862
alloc_fs_context+0x9a3/0xd00 fs/fs_context.c:295
do_remount fs/namespace.c:3392 [inline]
path_mount+0xc5e/0x1040 fs/namespace.c:4153
do_mount fs/namespace.c:4174 [inline]
__do_sys_mount fs/namespace.c:4390 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4367
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6026:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2677 [inline]
slab_free mm/slub.c:6377 [inline]
kfree+0x1c5/0x6c0 mm/slub.c:6692
put_fs_context+0x123/0xb00 fs/fs_context.c:498
do_remount fs/namespace.c:3419 [inline]
path_mount+0xef9/0x1040 fs/namespace.c:4153
do_mount fs/namespace.c:4174 [inline]
__do_sys_mount fs/namespace.c:4390 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4367
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888030028d00
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 28 bytes inside of
freed 32-byte region [ffff888030028d00, ffff888030028d20)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x30028
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff88813ffb2780 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800400040 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2774, tgid 2774 (kworker/u8:4), ts 16704250728, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
prep_new_page mm/page_alloc.c:1867 [inline]
get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
alloc_slab_page mm/slub.c:3266 [inline]
allocate_slab+0x79/0x5e0 mm/slub.c:3380
new_slab mm/slub.c:3426 [inline]
refill_objects+0x2d8/0x350 mm/slub.c:7310
refill_sheaf mm/slub.c:2804 [inline]
__pcs_replace_empty_main+0x330/0x690 mm/slub.c:4675
alloc_from_pcs mm/slub.c:4773 [inline]
slab_alloc_node mm/slub.c:4905 [inline]
__kmalloc_cache_noprof+0x468/0x6b0 mm/slub.c:5485
_kmalloc_noprof include/linux/slab.h:988 [inline]
slab_free_hook mm/slub.c:2629 [inline]
slab_free mm/slub.c:6377 [inline]
kmem_cache_free+0x156/0x6c0 mm/slub.c:6504
__fput_deferred+0x2df/0x3e0 fs/file_table.c:567
fput_close+0x11f/0x240 fs/file_table.c:629
path_openat+0x30d5/0x3850 fs/namei.c:4872
do_file_open+0x23e/0x4a0 fs/namei.c:4892
do_open_execat+0x12b/0x590 fs/exec.c:785
alloc_bprm+0x24/0x640 fs/exec.c:1431
class_bprm_constructor fs/exec.c:1497 [inline]
kernel_execve+0x85/0x9c0 fs/exec.c:1889
call_usermodehelper_exec_async+0x212/0x360 kernel/umh.c:109
page_owner free stack trace missing

Memory state around the buggy address:
ffff888030028c00: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
ffff888030028c80: 00 00 00 fc fc fc fc fc fa fb fb fb fc fc fc fc
>ffff888030028d00: fa fb fb fb fc fc fc fc 00 00 04 fc fc fc fc fc
^
ffff888030028d80: 00 00 07 fc fc fc fc fc 00 00 07 fc fc fc fc fc
ffff888030028e00: 00 00 00 fc fc fc fc fc 00 00 00 fc fc fc fc fc
==================================================================


---
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[Edward Adam Davis]

#syz test: upstream master

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 3305fe406cb2..58540491e68b 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -461,7 +461,7 @@ static int ntfs_fs_reconfigure(struct fs_context *fc)
}

sync_filesystem(sb);
- swap(sbi->options, fc->fs_private);
+ memcpy(sbi->options, fc->fs_private, sizeof(*sbi->options));

return 0;
}