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)

Affected Software

References

• https://git.kernel.org/stable/c/2064bc663f89e61b8681c1fb9d1ce445de72063d
• https://git.kernel.org/stable/c/64bb6000bfbdf241a6dd578199acd90321a4243e
• https://git.kernel.org/stable/c/66c074eab6f966fbe48a0fc4b3a45b2a2e2df527
• https://git.kernel.org/stable/c/72caafbc95c5dca8266a942b8e96ad81d8d9adc7
• https://git.kernel.org/stable/c/94fce1d3e74fe011e21f17490ba58491709fd7e5
• https://git.kernel.org/stable/c/bd631e2005290a55c8edda87363bc0d594c01705
• https://git.kernel.org/stable/c/eb80003744e32a7366a523015e4acfe0a2ac7d88