selinux: cleanup and consolidate the XFRM alloc/clone/delete/free code

The SELinux labeled IPsec code state management functions have been
long neglected and could use some cleanup and consolidation.
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

security/selinux/xfrm.c

@@ -121,6 +121,33 @@ static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
 	return rc;
 }
 
+/*
+ * Free the xfrm_sec_ctx structure.
+ */
+static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
+{
+	if (!ctx)
+		return;
+
+	atomic_dec(&selinux_xfrm_refcount);
+	kfree(ctx);
+}
+
+/*
+ * Authorize the deletion of a labeled SA or policy rule.
+ */
+static int selinux_xfrm_delete(struct xfrm_sec_ctx *ctx)
+{
+	const struct task_security_struct *tsec = current_security();
+
+	if (!ctx)
+		return 0;
+
+	return avc_has_perm(tsec->sid, ctx->ctx_sid,
+			    SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
+			    NULL);
+}
+
 /*
  * LSM hook implementation that authorizes that a flow can use
  * a xfrm policy rule.
@@ -258,17 +285,16 @@ int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
 {
 	struct xfrm_sec_ctx *new_ctx;
 
-	if (old_ctx) {
-		new_ctx = kmalloc(sizeof(*old_ctx) + old_ctx->ctx_len,
-				  GFP_ATOMIC);
+	if (!old_ctx)
+		return 0;
+
+	new_ctx = kmalloc(sizeof(*old_ctx) + old_ctx->ctx_len, GFP_ATOMIC);
 	if (!new_ctx)
 		return -ENOMEM;
-
-		memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
-		memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
+	memcpy(new_ctx, old_ctx, sizeof(*old_ctx) + old_ctx->ctx_len);
 	atomic_inc(&selinux_xfrm_refcount);
 	*new_ctxp = new_ctx;
-	}
+
 	return 0;
 }
 
@@ -277,8 +303,7 @@ int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
  */
 void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
 {
-	atomic_dec(&selinux_xfrm_refcount);
-	kfree(ctx);
+	selinux_xfrm_free(ctx);
 }
 
 /*
@@ -286,14 +311,7 @@ void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
  */
 int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx)
 {
-	const struct task_security_struct *tsec = current_security();
-
-	if (!ctx)
-		return 0;
-
-	return avc_has_perm(tsec->sid, ctx->ctx_sid,
-			    SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
-			    NULL);
+	return selinux_xfrm_delete(ctx);
 }
 
 /*
@@ -349,8 +367,7 @@ int selinux_xfrm_state_alloc_acquire(struct xfrm_state *x,
  */
 void selinux_xfrm_state_free(struct xfrm_state *x)
 {
-	atomic_dec(&selinux_xfrm_refcount);
-	kfree(x->security);
+	selinux_xfrm_free(x->security);
 }
 
  /*
@@ -358,15 +375,7 @@ void selinux_xfrm_state_free(struct xfrm_state *x)
   */
 int selinux_xfrm_state_delete(struct xfrm_state *x)
 {
-	const struct task_security_struct *tsec = current_security();
-	struct xfrm_sec_ctx *ctx = x->security;
-
-	if (!ctx)
-		return 0;
-
-	return avc_has_perm(tsec->sid, ctx->ctx_sid,
-			    SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
-			    NULL);
+	return selinux_xfrm_delete(x->security);
 }
 
 /*