[PATCH v39 21/42] LSM: security_lsmblob_to_secctx module selection

[Casey Schaufler]

Add a parameter lsmid to security_lsmblob_to_secctx() to identify which
of the security modules that may be active should provide the security
context. If the value of lsmid is LSM_ID_UNDEF the first LSM providing
a hook is used. security_secid_to_secctx() is unchanged, and will
always report the first LSM providing a hook.

Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
---
 include/linux/security.h     |  5 +++--
 kernel/audit.c               |  4 ++--
 kernel/auditsc.c             |  8 +++++---
 net/netlabel/netlabel_user.c |  3 ++-
 security/security.c          | 11 ++++++-----
 5 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 35604f43d4ff..360a454d5f8e 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -563,7 +563,8 @@ int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
 int security_netlink_send(struct sock *sk, struct sk_buff *skb);
 int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, struct lsmcontext *cp);
-int security_lsmblob_to_secctx(struct lsmblob *blob, struct lsmcontext *cp);
+int security_lsmblob_to_secctx(struct lsmblob *blob, struct lsmcontext *cp,
+			       int lsmid);
 int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
 void security_release_secctx(struct lsmcontext *cp);
 void security_inode_invalidate_secctx(struct inode *inode);
@@ -1491,7 +1492,7 @@ static inline int security_secid_to_secctx(u32 secid, struct lsmcontext *cp)
 }
 
 static inline int security_lsmblob_to_secctx(struct lsmblob *blob,
-					     struct lsmcontext *cp)
+					     struct lsmcontext *cp, int lsmid)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/kernel/audit.c b/kernel/audit.c
index a93a710c980e..edefb370a72e 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1462,7 +1462,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 
 		if (lsmblob_is_set(&audit_sig_lsm)) {
 			err = security_lsmblob_to_secctx(&audit_sig_lsm,
-							 &lsmctx);
+							 &lsmctx, LSM_ID_UNDEF);
 			if (err < 0)
 				return err;
 		}
@@ -2174,7 +2174,7 @@ int audit_log_task_context(struct audit_buffer *ab)
 	if (!lsmblob_is_set(&blob))
 		return 0;
 
-	error = security_lsmblob_to_secctx(&blob, &ctx);
+	error = security_lsmblob_to_secctx(&blob, &ctx, LSM_ID_UNDEF);
 	if (error < 0) {
 		if (error != -EINVAL)
 			goto error_path;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index c37cc02ea4cc..3c0559b01677 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1109,7 +1109,7 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
 			 from_kuid(&init_user_ns, auid),
 			 from_kuid(&init_user_ns, uid), sessionid);
 	if (lsmblob_is_set(blob)) {
-		if (security_lsmblob_to_secctx(blob, &ctx) < 0) {
+		if (security_lsmblob_to_secctx(blob, &ctx, LSM_ID_UNDEF) < 0) {
 			audit_log_format(ab, " obj=(none)");
 			rc = 1;
 		} else {
@@ -1394,7 +1394,8 @@ static void show_special(struct audit_context *context, int *call_panic)
 				 context->ipc.mode);
 		if (lsmblob_is_set(&context->ipc.oblob)) {
 			if (security_lsmblob_to_secctx(&context->ipc.oblob,
-						       &lsmctx) < 0) {
+						       &lsmctx,
+						       LSM_ID_UNDEF) < 0) {
 				*call_panic = 1;
 			} else {
 				audit_log_format(ab, " obj=%s", lsmctx.context);
@@ -1559,7 +1560,8 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
 	if (lsmblob_is_set(&n->oblob)) {
 		struct lsmcontext ctx;
 
-		if (security_lsmblob_to_secctx(&n->oblob, &ctx) < 0) {
+		if (security_lsmblob_to_secctx(&n->oblob, &ctx,
+					       LSM_ID_UNDEF) < 0) {
 			if (call_panic)
 				*call_panic = 2;
 		} else {
diff --git a/net/netlabel/netlabel_user.c b/net/netlabel/netlabel_user.c
index 561e1e476a49..842a236540b0 100644
--- a/net/netlabel/netlabel_user.c
+++ b/net/netlabel/netlabel_user.c
@@ -98,7 +98,8 @@ struct audit_buffer *netlbl_audit_start_common(int type,
 			 audit_info->sessionid);
 
 	if (lsmblob_is_set(&audit_info->blob) &&
-	    security_lsmblob_to_secctx(&audit_info->blob, &ctx) >= 0) {
+	    security_lsmblob_to_secctx(&audit_info->blob, &ctx,
+				       LSM_ID_UNDEF) >= 0) {
 		audit_log_format(audit_buf, " subj=%s", ctx.context);
 		security_release_secctx(&ctx);
 	}
diff --git a/security/security.c b/security/security.c
index cea3c1b614a1..444051575793 100644
--- a/security/security.c
+++ b/security/security.c
@@ -4203,6 +4203,7 @@ EXPORT_SYMBOL(security_secid_to_secctx);
  * security_lsmblob_to_secctx() - Convert a lsmblob to a secctx
  * @blob: lsm specific information
  * @cp: the LSM context
+ * @lsmid: which security module to report
  *
  * Convert a @blob entry to security context. If @cp is NULL the
  * length of the result will be returned, but no data will be returned.
@@ -4212,15 +4213,15 @@ EXPORT_SYMBOL(security_secid_to_secctx);
  *
  * Return: Return length of data on success, error on failure.
  */
-int security_lsmblob_to_secctx(struct lsmblob *blob, struct lsmcontext *cp)
+int security_lsmblob_to_secctx(struct lsmblob *blob, struct lsmcontext *cp,
+			       int lsmid)
 {
 	struct security_hook_list *hp;
-	int rc;
 
 	hlist_for_each_entry(hp, &security_hook_heads.lsmblob_to_secctx, list) {
-		rc = hp->hook.lsmblob_to_secctx(blob, cp);
-		if (rc != LSM_RET_DEFAULT(lsmblob_to_secctx))
-			return rc;
+		if (lsmid != hp->lsmid->id && lsmid != LSM_ID_UNDEF)
+			continue;
+		return hp->hook.lsmblob_to_secctx(blob, cp);
 	}
 
 	return LSM_RET_DEFAULT(lsmblob_to_secctx);
-- 
2.41.0