From 45d1a9ae772acdf1291c0880217beb16d3bc60c7 Mon Sep 17 00:00:00 2001
From: Philippe Antoine <contact@catenacyber.fr>
Date: Mon, 5 Jul 2021 17:05:10 +0200
Subject: [PATCH] detect: faster linked list copy

In DetectAppLayerInspectEngineCopyListToDetectCtx
Avoid quadratic complexity by remembering last element
of the linked list we are inserting into
---
 src/detect-engine-mpm.c | 11 +++++------
 src/detect-engine.c     |  9 +++------
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/src/detect-engine-mpm.c b/src/detect-engine-mpm.c
index 2d55e709ed..9d126c7ed6 100644
--- a/src/detect-engine-mpm.c
+++ b/src/detect-engine-mpm.c
@@ -215,6 +215,7 @@ void DetectAppLayerMpmRegisterByParentId(DetectEngineCtx *de_ctx,
 void DetectMpmInitializeAppMpms(DetectEngineCtx *de_ctx)
 {
     const DetectBufferMpmRegistery *list = g_mpm_list[DETECT_BUFFER_MPM_TYPE_APP];
+    DetectBufferMpmRegistery *toadd = de_ctx->app_mpms_list;
     while (list != NULL) {
         DetectBufferMpmRegistery *n = SCCalloc(1, sizeof(*n));
         BUG_ON(n == NULL);
@@ -222,14 +223,12 @@ void DetectMpmInitializeAppMpms(DetectEngineCtx *de_ctx)
         *n = *list;
         n->next = NULL;
 
-        if (de_ctx->app_mpms_list == NULL) {
+        if (toadd == NULL) {
+            toadd = n;
             de_ctx->app_mpms_list = n;
         } else {
-            DetectBufferMpmRegistery *t = de_ctx->app_mpms_list;
-            while (t->next != NULL) {
-                t = t->next;
-            }
-            t->next = n;
+            toadd->next = n;
+            toadd = toadd->next;
         }
 
         /* default to whatever the global setting is */
diff --git a/src/detect-engine.c b/src/detect-engine.c
index 000fed2112..9d7fd2a49a 100644
--- a/src/detect-engine.c
+++ b/src/detect-engine.c
@@ -322,6 +322,7 @@ static void DetectAppLayerInspectEngineCopy(
 static void DetectAppLayerInspectEngineCopyListToDetectCtx(DetectEngineCtx *de_ctx)
 {
     const DetectEngineAppInspectionEngine *t = g_app_inspect_engines;
+    DetectEngineAppInspectionEngine *list = de_ctx->app_inspect_engines;
     while (t) {
         DetectEngineAppInspectionEngine *new_engine = SCCalloc(1, sizeof(DetectEngineAppInspectionEngine));
         if (unlikely(new_engine == NULL)) {
@@ -334,16 +335,12 @@ static void DetectAppLayerInspectEngineCopyListToDetectCtx(DetectEngineCtx *de_c
         new_engine->progress = t->progress;
         new_engine->v2 = t->v2;
 
-        if (de_ctx->app_inspect_engines == NULL) {
+        if (list == NULL) {
             de_ctx->app_inspect_engines = new_engine;
         } else {
-            DetectEngineAppInspectionEngine *list = de_ctx->app_inspect_engines;
-            while (list->next != NULL) {
-                list = list->next;
-            }
-
             list->next = new_engine;
         }
+        list = new_engine;
 
         t = t->next;
     }