CVE-2026-68148

Description

In the Linux kernel, the following vulnerability has been resolved: fscrypt: Add missing superblock check in find_or_insert_direct_key() The legacy -fscrypt_direct_keys- table caches master keys that are used by v1 encryption policies that have FSCRYPT_POLICY_FLAG_DIRECT_KEY. It-s just a global table for all filesystems (since the keys can be provided by the legacy process-subscribed keyrings mechanism, which makes it difficult to reuse super_block::s_master_keys). The entries in it (-struct fscrypt_direct_key-) do contain a super_block pointer, though, for passing to fscrypt_destroy_inline_crypt_key() when the last inode that references the key is evicted. However, when finding the fscrypt_direct_key for an inode, we weren-t actually comparing the super_block pointer. As a result, inodes with different super_blocks could point to the same fscrypt_direct_key. That could extend the lifetime of a fscrypt_direct_key beyond the super_block it points to, causing a use-after-free later. Fix this by creating distinct fscrypt_direct_key structs for distinct super_block structs. Note that this problem doesn-t exist in the v2 policy equivalent (-per-mode keys-), since the data structures there are per super_block.