CVE-2026-89785

In the Linux kernel, the following vulnerability has been resolved:

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

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)