Re: [PATCH] ntfs3: fix info-leak in ntfs_rename()

[Konstantin Komarov <almaz.alexandrovich@paragon-software.com>]

On 6/10/26 13:12, Dmitry Antipov wrote:

> On Wed, 2026-06-10 at 00:08 +0100, Al Viro wrote:
>
>>  From the syzkaller spew it would appear that data (filename converted
>> to unicode, AFAICS) somehow gets returned by read(2).  If that is
>> accurate, I would suggest that the things are already FUBAR and zeroing
>> is not going to fix whatever underlying bug you've got there (metadata
>> bh left around after the corresponding on-disk block got freed and
>> reused for regular file, perhaps?)
> Hard to say about copy_to_user_iter(), but at least the first splat
> looks correct. At the end of fill_name_de(), data layout is:
>
> struct NTFS_DE *e = buf;
> ...
>
>      |<- data_size + sizeof(struct NTFS_DE) ->|<- XXX ->|
> buf |-----------------------------------------------------------
>      |<- ALIGN(data_size, 8) + sizeof(struct NTFS_DE) ->|   ;; e->size
>
> If 'buf' was allocated with kmalloc(), XXX remains uninitialized and
> passed as such to memcpy() called from hdr_insert_de().
>
> So using kzalloc() for all buffers passed to fill_name_de() looks
> the simplest and most safe solution. OTOH if someone would have
> said that an overhead of PAGE_SIZE'd memset() is too large, more
> fine-granted solution is to memset() XXX only, i.e.:
>
> diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
> index b2af8f695e60..21e4a2a34389 100644
> --- a/fs/ntfs3/namei.c
> +++ b/fs/ntfs3/namei.c
> @@ -22,7 +22,7 @@ int fill_name_de(struct ntfs_sb_info *sbi, void *buf, const struct qstr *name,
>   {
>          int err;
>          struct NTFS_DE *e = buf;
> -       u16 data_size;
> +       u16 data_size, real_size, aligned_size;
>          struct ATTR_FILE_NAME *fname = (struct ATTR_FILE_NAME *)(e + 1);
>   
>   #ifndef CONFIG_NTFS3_64BIT_CLUSTER
> @@ -53,7 +53,12 @@ int fill_name_de(struct ntfs_sb_info *sbi, void *buf, const struct qstr *name,
>          fname->type = FILE_NAME_POSIX;
>          data_size = fname_full_size(fname);
>   
> -       e->size = cpu_to_le16(ALIGN(data_size, 8) + sizeof(struct NTFS_DE));
> +       real_size = data_size + sizeof(struct NTFS_DE);
> +       aligned_size = ALIGN(data_size, 8) + sizeof(struct NTFS_DE);
> +       if (aligned_size > real_size)
> +               memset((char *)buf + real_size, 0, aligned_size - real_size);
> +
> +       e->size = cpu_to_le16(aligned_size);
>          e->key_size = cpu_to_le16(data_size);
>          e->flags = 0;
>          e->res = 0;
>
> Dmitry

Hello,

Very sorry for the delay.
The patch is applied, thank you.

Regards,
Konstantin