lsm: security_lsmblob_to_secctx module selection

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@schaufler-ca.com>
[PM: subj tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>

include/linux/security.h

@@ -567,7 +567,8 @@ int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
 int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
 int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, struct lsm_context *cp);
-int security_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp);
+int security_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp,
+			       int lsmid);
 int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
 void security_release_secctx(struct lsm_context *cp);
 void security_inode_invalidate_secctx(struct inode *inode);
@@ -1551,7 +1552,8 @@ static inline int security_secid_to_secctx(u32 secid, struct lsm_context *cp)
 }
 
 static inline int security_lsmprop_to_secctx(struct lsm_prop *prop,
-					     struct lsm_context *cp)
+					     struct lsm_context *cp,
+					     int lsmid)
 {
 	return -EOPNOTSUPP;
 }

kernel/audit.c

@@ -1473,7 +1473,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 	case AUDIT_SIGNAL_INFO:
 		if (lsmprop_is_set(&audit_sig_lsm)) {
 			err = security_lsmprop_to_secctx(&audit_sig_lsm,
-							 &lsmctx);
+							 &lsmctx, LSM_ID_UNDEF);
 			if (err < 0)
 				return err;
 		}
@@ -2188,7 +2188,7 @@ int audit_log_task_context(struct audit_buffer *ab)
 	if (!lsmprop_is_set(&prop))
 		return 0;
 
-	error = security_lsmprop_to_secctx(&prop, &ctx);
+	error = security_lsmprop_to_secctx(&prop, &ctx, LSM_ID_UNDEF);
 	if (error < 0) {
 		if (error != -EINVAL)
 			goto error_path;

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 (lsmprop_is_set(prop)) {
-		if (security_lsmprop_to_secctx(prop, &ctx) < 0) {
+		if (security_lsmprop_to_secctx(prop, &ctx, LSM_ID_UNDEF) < 0) {
 			audit_log_format(ab, " obj=(none)");
 			rc = 1;
 		} else {
@@ -1395,7 +1395,8 @@ static void show_special(struct audit_context *context, int *call_panic)
 			struct lsm_context lsmctx;
 
 			if (security_lsmprop_to_secctx(&context->ipc.oprop,
-						       &lsmctx) < 0) {
+						       &lsmctx,
+						       LSM_ID_UNDEF) < 0) {
 				*call_panic = 1;
 			} else {
 				audit_log_format(ab, " obj=%s", lsmctx.context);
@@ -1560,7 +1561,8 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
 	if (lsmprop_is_set(&n->oprop)) {
 		struct lsm_context ctx;
 
-		if (security_lsmprop_to_secctx(&n->oprop, &ctx) < 0) {
+		if (security_lsmprop_to_secctx(&n->oprop, &ctx,
+					       LSM_ID_UNDEF) < 0) {
 			if (call_panic)
 				*call_panic = 2;
 		} else {

net/netlabel/netlabel_user.c

@@ -98,7 +98,8 @@ struct audit_buffer *netlbl_audit_start_common(int type,
 			 audit_info->sessionid);
 
 	if (lsmprop_is_set(&audit_info->prop) &&
-	    security_lsmprop_to_secctx(&audit_info->prop, &ctx) > 0) {
+	    security_lsmprop_to_secctx(&audit_info->prop, &ctx,
+				       LSM_ID_UNDEF) > 0) {
 		audit_log_format(audit_buf, " subj=%s", ctx.context);
 		security_release_secctx(&ctx);
 	}

security/security.c

@@ -4342,17 +4342,31 @@ EXPORT_SYMBOL(security_secid_to_secctx);
  * security_lsmprop_to_secctx() - Convert a lsm_prop to a secctx
  * @prop: lsm specific information
  * @cp: the LSM context
+ * @lsmid: which security module to report
  *
  * Convert a @prop entry to security context.  If @cp is NULL the
  * length of the result will be returned. This does mean that the
  * length could change between calls to check the length and the
  * next call which actually allocates and returns the @cp.
  *
+ * @lsmid identifies which LSM should supply the context.
+ * A value of LSM_ID_UNDEF indicates that the first LSM suppling
+ * the hook should be used. This is used in cases where the
+ * ID of the supplying LSM is unambiguous.
+ *
  * Return: Return length of data on success, error on failure.
  */
-int security_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp)
+int security_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp,
+			       int lsmid)
 {
-	return call_int_hook(lsmprop_to_secctx, prop, cp);
+	struct lsm_static_call *scall;
+
+	lsm_for_each_hook(scall, lsmprop_to_secctx) {
+		if (lsmid != LSM_ID_UNDEF && lsmid != scall->hl->lsmid->id)
+			continue;
+		return scall->hl->hook.lsmprop_to_secctx(prop, cp);
+	}
+	return LSM_RET_DEFAULT(lsmprop_to_secctx);
 }
 EXPORT_SYMBOL(security_lsmprop_to_secctx);