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

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

[Weiming Shi]

From: Weiming Wu <weiming3@asu.edu>

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 <xmei5@asu.edu>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
 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

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

[Konstantin Komarov]

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

> From: Weiming Wu <weiming3@asu.edu>
>
> 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 <xmei5@asu.edu>
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Weiming Shi <bestswngs@gmail.com>
> ---
>   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

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

[Weiming Shi]

Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
于2026年7月15日周三 00:45写道：
>
> On 6/10/26 13:57, Weiming Shi wrote:
>
> > From: Weiming Wu <weiming3@asu.edu>
> >
> > 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 <xmei5@asu.edu>
> > Assisted-by: Claude:claude-opus-4-8
> > Signed-off-by: Weiming Shi <bestswngs@gmail.com>
> > ---
> >   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
>

Hi Konstantin,

Thank you for the update and for applying the patch.

Best regards,
Weiming Shi