[PATCH V34 02/29] security: Add a "locked down" LSM hook

Matthew Garrett
2019-06-22T00:04:09Z

Add a mechanism to allow LSMs to make a policy decision around whether
kernel functionality that would allow tampering with or examining the
runtime state of the kernel should be permitted.

Signed-off-by: Matthew Garrett <mjg59@google.com>
---
include/linux/lsm_hooks.h | 2 ++
include/linux/security.h | 11 +++++++++++
security/security.c | 6 ++++++
3 files changed, 19 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 66fd1eac7a32..df2aebc99838 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1790,6 +1790,7 @@ union security_list_options {
int (*bpf_prog_alloc_security)(struct bpf_prog_aux *aux);
void (*bpf_prog_free_security)(struct bpf_prog_aux *aux);
#endif /* CONFIG_BPF_SYSCALL */
+ int (*locked_down)(enum lockdown_reason what);
};

struct security_hook_heads {
@@ -2027,6 +2028,7 @@ struct security_hook_heads {
struct hlist_head bpf_prog_alloc_security;
struct hlist_head bpf_prog_free_security;
#endif /* CONFIG_BPF_SYSCALL */
+ struct hlist_head locked_down;
} __randomize_layout;

/*
diff --git a/include/linux/security.h b/include/linux/security.h
index 1bb6fb2f1523..9eaf02e70707 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -76,6 +76,12 @@ enum lsm_event {
LSM_POLICY_CHANGE,
};

+enum lockdown_reason {
+ LOCKDOWN_NONE,
+ LOCKDOWN_INTEGRITY_MAX,
+ LOCKDOWN_CONFIDENTIALITY_MAX,
+};
+
/* These functions are in security/commoncap.c */
extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
int cap, unsigned int opts);
@@ -389,6 +395,7 @@ void security_inode_invalidate_secctx(struct inode *inode);
int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
+int security_locked_down(enum lockdown_reason what);
#else /* CONFIG_SECURITY */

static inline int call_lsm_notifier(enum lsm_event event, void *data)
@@ -1189,6 +1196,10 @@ static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32
{
return -EOPNOTSUPP;
}
+static inline int security_locked_down(enum lockdown_reason what)
+{
+ return 0;
+}
#endif /* CONFIG_SECURITY */

#ifdef CONFIG_SECURITY_NETWORK
diff --git a/security/security.c b/security/security.c
index 487e1f3eb2df..553f50e9a106 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2382,3 +2382,9 @@ void security_bpf_prog_free(struct bpf_prog_aux *aux)
call_void_hook(bpf_prog_free_security, aux);
}
#endif /* CONFIG_BPF_SYSCALL */
+
+int security_locked_down(enum lockdown_reason what)
+{
+ return call_int_hook(locked_down, 0, what);
+}
+EXPORT_SYMBOL(security_locked_down);
--
2.22.0.410.gd8fdbe21b5-goog