Re: [PATCH] fs/ntfs3: fix out-of-bounds read of INDEX_ROOT in reparse/objid init

On 6/10/26 13:57, Weiming Shi wrote:

> From: Weiming Wu <[email protected]>
>
> ntfs_reparse_init() and ntfs_objid_init() parse the index root of the
> $Extend/$Reparse and $Extend/$ObjId metafiles (the INDEX_ROOT attributes
> named $R and $O). They read its type and rule fields through
> resident_data(), which does not check that the resident attribute is
> large enough to hold them.
>
> mi_enum_attr() accepts a resident attribute with data_off == asize and
> data_size == 0. For such an attribute placed last in its MFT record,
> resident_data() returns a pointer to the end of the record_size buffer,
> so reading root->type / root->rule reads past the allocation.
>
> Use resident_data_ex(attr, sizeof(struct INDEX_ROOT)) and bail out when
> it returns NULL, as ntfs_security_init() already does for $SDH / $SII.
>
> The attribute is only parsed while mounting a crafted image, so this
> needs CAP_SYS_ADMIN.
>
>   BUG: KASAN: slab-out-of-bounds in ntfs_reparse_init (fs/ntfs3/fsntfs.c:2306)
>   Read of size 4 at addr ffff88801219dc00 by task mount
>    ntfs_reparse_init (fs/ntfs3/fsntfs.c:2306)
>    ntfs_fill_super (fs/ntfs3/super.c:1604)
>    get_tree_bdev_flags (fs/super.c:1703)
>    vfs_get_tree (fs/super.c:1758)
>    path_mount (fs/namespace.c:4131)
>    __x64_sys_mount (fs/namespace.c:4360)
>
> Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
> Reported-by: Xiang Mei <[email protected]>
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Weiming Shi <[email protected]>
> ---
>   fs/ntfs3/fsntfs.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ntfs3/fsntfs.c b/fs/ntfs3/fsntfs.c
> index d0434756029b6..42493a2da24ef 100644
> --- a/fs/ntfs3/fsntfs.c
> +++ b/fs/ntfs3/fsntfs.c
> @@ -2302,8 +2302,8 @@ int ntfs_reparse_init(struct ntfs_sb_info *sbi)
>                  goto out;
>          }
>
> -       root_r = resident_data(attr);
> -       if (root_r->type != ATTR_ZERO ||
> +       root_r = resident_data_ex(attr, sizeof(struct INDEX_ROOT));
> +       if (!root_r || root_r->type != ATTR_ZERO ||
>              root_r->rule != NTFS_COLLATION_TYPE_UINTS) {
>                  err = -EINVAL;
>                  goto out;
> @@ -2340,8 +2340,8 @@ int ntfs_objid_init(struct ntfs_sb_info *sbi)
>                  goto out;
>          }
>
> -       root = resident_data(attr);
> -       if (root->type != ATTR_ZERO ||
> +       root = resident_data_ex(attr, sizeof(struct INDEX_ROOT));
> +       if (!root || root->type != ATTR_ZERO ||
>              root->rule != NTFS_COLLATION_TYPE_UINTS) {
>                  err = -EINVAL;
>                  goto out;
> --
> 2.43.0
>
Hello,

Very sorry for the delay.
Your patch was applied, thank you.

Regards,
Konstantin