bugfix: use of the ngx.re API might lead to errors like "pcre_compile() failed: failed to get memory" due to incorrect pcre_malloc and pcre_free handling. thanks Vittly for reporting this in github issue #72.

Author: agentzh

src/ngx_http_lua_headerfilterby.c

@@ -101,6 +101,9 @@ ngx_http_lua_header_filter_by_chunk(lua_State *L, ngx_http_request_t *r)
 {
     ngx_int_t        rc;
     u_char          *err_msg;
+#if (NGX_PCRE)
+    ngx_pool_t      *old_pool;
+#endif
 
     /*  set Lua VM panic handler */
     lua_atpanic(L, ngx_http_lua_atpanic);
@@ -110,15 +113,15 @@ ngx_http_lua_header_filter_by_chunk(lua_State *L, ngx_http_request_t *r)
 
 #if (NGX_PCRE)
     /* XXX: work-around to nginx regex subsystem */
-    ngx_http_lua_pcre_malloc_init(r->pool);
+    old_pool = ngx_http_lua_pcre_malloc_init(r->pool);
 #endif
 
     /*  protected call user code */
     rc = lua_pcall(L, 0, 1, 0);
 
 #if (NGX_PCRE)
     /* XXX: work-around to nginx regex subsystem */
-    ngx_http_lua_pcre_malloc_done();
+    ngx_http_lua_pcre_malloc_done(old_pool);
 #endif
 
     if (rc != 0) {

src/ngx_http_lua_pcrefix.c

@@ -4,10 +4,11 @@
 #include "ddebug.h"
 
 #include "ngx_http_lua_pcrefix.h"
+#include "stdio.h"
 
 #if (NGX_PCRE)
 
-ngx_pool_t *ngx_http_lua_pcre_pool;
+static ngx_pool_t *ngx_http_lua_pcre_pool = NULL;
 
 static void *(*old_pcre_malloc)(size_t);
 static void (*old_pcre_free)(void *ptr);
@@ -17,48 +18,79 @@ static void (*old_pcre_free)(void *ptr);
  * to use PCRE functions. As PCRE still has memory-leaking problems,
  * and nginx overwrote pcre_malloc/free hooks with its own static
  * functions, so nobody else can reuse nginx regex subsystem... */
-void *
+static void *
 ngx_http_lua_pcre_malloc(size_t size)
 {
-	if (ngx_http_lua_pcre_pool) {
-		return ngx_palloc(ngx_http_lua_pcre_pool, size);
-	}
+    dd("lua pcre pool is %p", ngx_http_lua_pcre_pool);
 
-    dd("returning NULL");
+    if (ngx_http_lua_pcre_pool) {
+        return ngx_palloc(ngx_http_lua_pcre_pool, size);
+    }
 
-	return NULL;
+    fprintf(stderr, "error: lua pcre malloc failed due to empty pcre pool");
+
+    return NULL;
 }
 
 
 static void
 ngx_http_lua_pcre_free(void *ptr)
 {
-	if (ngx_http_lua_pcre_pool) {
-		ngx_pfree(ngx_http_lua_pcre_pool, ptr);
-	}
+    dd("lua pcre pool is %p", ngx_http_lua_pcre_pool);
+
+    if (ngx_http_lua_pcre_pool) {
+        ngx_pfree(ngx_http_lua_pcre_pool, ptr);
+        return;
+    }
+
+    fprintf(stderr, "error: lua pcre free failed due to empty pcre pool");
 }
 
 
-void
+ngx_pool_t *
 ngx_http_lua_pcre_malloc_init(ngx_pool_t *pool)
 {
-	ngx_http_lua_pcre_pool = pool;
+    ngx_pool_t          *old_pool;
+
+    if (pcre_malloc != ngx_http_lua_pcre_malloc) {
+
+        dd("overriding nginx pcre malloc and free");
+
+        ngx_http_lua_pcre_pool = pool;
 
-	old_pcre_malloc = pcre_malloc;
-	old_pcre_free = pcre_free;
+        old_pcre_malloc = pcre_malloc;
+        old_pcre_free = pcre_free;
 
-    pcre_malloc = ngx_http_lua_pcre_malloc;
-    pcre_free = ngx_http_lua_pcre_free;
+        pcre_malloc = ngx_http_lua_pcre_malloc;
+        pcre_free = ngx_http_lua_pcre_free;
+
+        return NULL;
+    }
+
+    dd("lua pcre pool was %p", ngx_http_lua_pcre_pool);
+
+    old_pool = ngx_http_lua_pcre_pool;
+    ngx_http_lua_pcre_pool = pool;
+
+    dd("lua pcre pool is %p", ngx_http_lua_pcre_pool);
+
+    return old_pool;
 }
 
 
 void
-ngx_http_lua_pcre_malloc_done()
+ngx_http_lua_pcre_malloc_done(ngx_pool_t *old_pool)
 {
-	ngx_http_lua_pcre_pool = NULL;
+    dd("lua pcre pool was %p", ngx_http_lua_pcre_pool);
+
+    ngx_http_lua_pcre_pool = old_pool;
+
+    dd("lua pcre pool is %p", ngx_http_lua_pcre_pool);
 
-	pcre_malloc = old_pcre_malloc;
-	pcre_free = old_pcre_free;
+    if (old_pool == NULL) {
+        pcre_malloc = old_pcre_malloc;
+        pcre_free = old_pcre_free;
+    }
 }
 
 #endif /* NGX_PCRE */

src/ngx_http_lua_pcrefix.h

@@ -6,11 +6,8 @@
 
 
 #if (NGX_PCRE)
-extern ngx_pool_t *ngx_http_lua_pcre_pool;
-
-void ngx_http_lua_pcre_malloc_init(ngx_pool_t *pool);
-void ngx_http_lua_pcre_malloc_done();
-void *ngx_http_lua_pcre_malloc(size_t size);
+ngx_pool_t *ngx_http_lua_pcre_malloc_init(ngx_pool_t *pool);
+void ngx_http_lua_pcre_malloc_done(ngx_pool_t *old_pool);
 #endif