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a6f0643e4f
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.
Fixes:
|
||
|---|---|---|
| .. | ||
| apparmor | ||
| bpf | ||
| integrity | ||
| ipe | ||
| keys | ||
| landlock | ||
| loadpin | ||
| lockdown | ||
| safesetid | ||
| selinux | ||
| smack | ||
| tomoyo | ||
| yama | ||
| commoncap_test.c | ||
| commoncap.c | ||
| device_cgroup.c | ||
| inode.c | ||
| Kconfig | ||
| Kconfig.hardening | ||
| lsm_audit.c | ||
| lsm_init.c | ||
| lsm_notifier.c | ||
| lsm_syscalls.c | ||
| lsm.h | ||
| Makefile | ||
| min_addr.c | ||
| security.c | ||