[PATCH v39 31/42] LSM: Exclusive secmark usage

[Casey Schaufler]

The network secmark can only be used by one security module
at a time. Establish mechanism to identify to security modules
whether they have access to the secmark. SELinux already
incorparates mechanism, but it has to be added to Smack and
AppArmor.

Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
---
 include/linux/lsm_hooks.h        |  1 +
 security/apparmor/include/net.h  |  5 +++++
 security/apparmor/lsm.c          |  7 ++++---
 security/security.c              |  6 ++++++
 security/selinux/hooks.c         |  4 +++-
 security/smack/smack.h           |  5 +++++
 security/smack/smack_lsm.c       |  3 ++-
 security/smack/smack_netfilter.c | 10 ++++++++--
 8 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 605aaf38c3f5..4deb1a4d2d1a 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -81,6 +81,7 @@ struct lsm_blob_sizes {
 	int	lbs_msg_msg;
 	int	lbs_task;
 	int	lbs_xattr_count; /* number of xattr slots in new_xattrs array */
+	bool	lbs_secmark;	/* expressed desire for secmark use */
 };
 
 /**
diff --git a/security/apparmor/include/net.h b/security/apparmor/include/net.h
index c42ed8a73f1c..2e43e1e8303c 100644
--- a/security/apparmor/include/net.h
+++ b/security/apparmor/include/net.h
@@ -51,6 +51,11 @@ struct aa_sk_ctx {
 	struct aa_label *peer;
 };
 
+static inline bool aa_secmark(void)
+{
+	return apparmor_blob_sizes.lbs_secmark;
+}
+
 static inline struct aa_sk_ctx *aa_sock(const struct sock *sk)
 {
 	return sk->sk_security + apparmor_blob_sizes.lbs_sock;
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 075942b253ae..ab9b0b37f1f7 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -1322,7 +1322,7 @@ static int apparmor_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
 	struct aa_sk_ctx *ctx = aa_sock(sk);
 
-	if (!skb->secmark)
+	if (!aa_secmark() || !skb->secmark)
 		return 0;
 
 	return apparmor_secmark_check(ctx->label, OP_RECVMSG, AA_MAY_RECEIVE,
@@ -1426,7 +1426,7 @@ static int apparmor_inet_conn_request(const struct sock *sk, struct sk_buff *skb
 {
 	struct aa_sk_ctx *ctx = aa_sock(sk);
 
-	if (!skb->secmark)
+	if (!aa_secmark() || !skb->secmark)
 		return 0;
 
 	return apparmor_secmark_check(ctx->label, OP_CONNECT, AA_MAY_CONNECT,
@@ -1442,6 +1442,7 @@ struct lsm_blob_sizes apparmor_blob_sizes __ro_after_init = {
 	.lbs_file = sizeof(struct aa_file_ctx),
 	.lbs_task = sizeof(struct aa_task_ctx),
 	.lbs_sock = sizeof(struct aa_sk_ctx),
+	.lbs_secmark = true,
 };
 
 static const struct lsm_id apparmor_lsmid = {
@@ -2105,7 +2106,7 @@ static unsigned int apparmor_ip_postroute(void *priv,
 	struct aa_sk_ctx *ctx;
 	struct sock *sk;
 
-	if (!skb->secmark)
+	if (!aa_secmark() || !skb->secmark)
 		return NF_ACCEPT;
 
 	sk = skb_to_full_sk(skb);
diff --git a/security/security.c b/security/security.c
index 3f0a4c5094a5..8469816c0472 100644
--- a/security/security.c
+++ b/security/security.c
@@ -232,6 +232,12 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 	lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
 	lsm_set_blob_size(&needed->lbs_xattr_count,
 			  &blob_sizes.lbs_xattr_count);
+	if (needed->lbs_secmark) {
+		if (!blob_sizes.lbs_secmark)
+			blob_sizes.lbs_secmark = true;
+		else
+			needed->lbs_secmark = false;
+	}
 }
 
 /* Prepare LSM for initialization. */
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a6deccbbcc40..3e590f632f59 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -164,7 +164,8 @@ __setup("checkreqprot=", checkreqprot_setup);
  */
 static int selinux_secmark_enabled(void)
 {
-	return (selinux_policycap_alwaysnetwork() ||
+	return selinux_blob_sizes.lbs_secmark &&
+	       (selinux_policycap_alwaysnetwork() ||
 		atomic_read(&selinux_secmark_refcount));
 }
 
@@ -6969,6 +6970,7 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
 	.lbs_sock = sizeof(struct sk_security_struct),
 	.lbs_superblock = sizeof(struct superblock_security_struct),
 	.lbs_xattr_count = SELINUX_INODE_INIT_XATTRS,
+	.lbs_secmark = true,
 };
 
 #ifdef CONFIG_PERF_EVENTS
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 297f21446f45..0f5bc5c03b9e 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -369,6 +369,11 @@ static inline int smk_inode_transmutable(const struct inode *isp)
 	return (sip->smk_flags & SMK_INODE_TRANSMUTE) != 0;
 }
 
+static inline bool smack_secmark(void)
+{
+	return smack_blob_sizes.lbs_secmark;
+}
+
 /*
  * Present a pointer to the smack label entry in an inode blob.
  */
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index a9ab31a40e36..c93e81facf1b 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4090,7 +4090,7 @@ static int smk_skb_to_addr_ipv6(struct sk_buff *skb, struct sockaddr_in6 *sip)
 #ifdef CONFIG_NETWORK_SECMARK
 static struct smack_known *smack_from_skb(struct sk_buff *skb)
 {
-	if (skb == NULL || skb->secmark == 0)
+	if (!smack_secmark() || skb == NULL || skb->secmark == 0)
 		return NULL;
 
 	return smack_from_secid(skb->secmark);
@@ -5064,6 +5064,7 @@ struct lsm_blob_sizes smack_blob_sizes __ro_after_init = {
 	.lbs_sock = sizeof(struct socket_smack),
 	.lbs_superblock = sizeof(struct superblock_smack),
 	.lbs_xattr_count = SMACK_INODE_INIT_XATTRS,
+	.lbs_secmark = true,
 };
 
 static const struct lsm_id smack_lsmid = {
diff --git a/security/smack/smack_netfilter.c b/security/smack/smack_netfilter.c
index bad71b7e648d..fd146e3a2286 100644
--- a/security/smack/smack_netfilter.c
+++ b/security/smack/smack_netfilter.c
@@ -26,7 +26,7 @@ static unsigned int smack_ip_output(void *priv,
 	struct socket_smack *ssp;
 	struct smack_known *skp;
 
-	if (sk) {
+	if (smack_secmark() && sk) {
 		ssp = smack_sock(sk);
 		skp = ssp->smk_out;
 		skb->secmark = skp->smk_secid;
@@ -54,12 +54,18 @@ static const struct nf_hook_ops smack_nf_ops[] = {
 
 static int __net_init smack_nf_register(struct net *net)
 {
+	if (!smack_secmark())
+		return 0;
+
 	return nf_register_net_hooks(net, smack_nf_ops,
 				     ARRAY_SIZE(smack_nf_ops));
 }
 
 static void __net_exit smack_nf_unregister(struct net *net)
 {
+	if (!smack_secmark())
+		return;
+
 	nf_unregister_net_hooks(net, smack_nf_ops, ARRAY_SIZE(smack_nf_ops));
 }
 
@@ -70,7 +76,7 @@ static struct pernet_operations smack_net_ops = {
 
 static int __init smack_nf_ip_init(void)
 {
-	if (smack_enabled == 0)
+	if (smack_enabled == 0 || !smack_secmark())
 		return 0;
 
 	printk(KERN_DEBUG "Smack: Registering netfilter hooks\n");
-- 
2.41.0