CVE-2026-64192

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

bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized

When CONFIG_BPF_LSM=y is set, BPF inode storage maps

(BPF_MAP_TYPE_INODE_STORAGE) are compiled into the kernel. However,

if the BPF LSM is not explicitly enabled at boot time (e.g. omitted

from the "lsm=" boot parameter), lsm_prepare() is never executed for

the BPF LSM.

Consequently, the BPF inode security blob offset

(bpf_lsm_blob_sizes.lbs_inode) is never initialized and remains at

its default compiled size of 8 bytes instead of being updated to a

valid offset past the reserved struct rcu_head (typically 16 bytes

or more).

When a privileged user creates and updates a BPF_MAP_TYPE_INODE_STORAGE

map, bpf_inode() evaluates inode->i_security + 8. This erroneously

aliases the struct rcu_head.func callback pointer at the beginning

of the inode->i_security blob. During subsequent map element cleanup

or inode destruction, writing NULL to owner_storage clears the queued

RCU callback pointer. When rcu_do_batch() later executes the queued

callback, it attempts an instruction fetch at address 0x0, triggering

an immediate kernel panic.

Fix this by introducing a global bpf_lsm_initialized boolean flag

marked with __ro_after_init. Set this flag to true inside bpf_lsm_init()

when the LSM framework successfully registers the BPF LSM. Gate map

allocation in inode_storage_map_alloc() on this flag, returning

-EOPNOTSUPP if the BPF LSM is in turn uninitialized.

This fail-fast approach prevents userspace from allocating inode

storage maps when the supporting BPF LSM infrastructure is absent,

avoiding zombie map states.