Introduce xfree_sized and xrealloc_sized

This will allow prism to pass buffer sizes to the Ruby GC.
It also helps avoid buffer overflow as it confirms the size was
correctly tracked all the way until the buffer is freed.

Author: byroot

Doxyfile

@@ -24,6 +24,7 @@ OUTPUT_DIRECTORY = doc
 JAVADOC_AUTOBRIEF = YES
 OPTIMIZE_OUTPUT_FOR_C = YES
 INPUT = src src/util include include/prism include/prism/util
+EXCLUDE = include/prism/debug_allocator.h
 HTML_OUTPUT = c
 SORT_MEMBER_DOCS = NO
 GENERATE_LATEX = NO

ext/prism/extension.c

@@ -413,7 +413,7 @@ dump(int argc, VALUE *argv, VALUE self) {
 if (options.freeze) rb_obj_freeze(value);
 
 #ifdefPRISM_BUILD_DEBUG
-xfree(dup);
+xfree_sized(dup, length);
 #endif
 
 pm_string_free(&input);
@@ -929,7 +929,7 @@ parse(int argc, VALUE *argv, VALUE self) {
 VALUEvalue=parse_input(&input, &options);
 
 #ifdefPRISM_BUILD_DEBUG
-xfree(dup);
+xfree_sized(dup, length);
 #endif
 
 pm_string_free(&input);

include/prism/debug_allocator.h

@@ -0,0 +1,99 @@
+/**
+ * @file debug_allocator.h
+ *
+ * Decorate allocation function to ensure sizes are correct.
+ */
+#ifndefPRISM_DEBUG_ALLOCATOR_H
+#definePRISM_DEBUG_ALLOCATOR_H
+
+#include<string.h>
+#include<stdio.h>
+#include<stdlib.h>
+
+staticinlinevoid*
+pm_debug_malloc(size_tsize)
+{
+size_t*memory=xmalloc(size+sizeof(size_t));
+memory[0] =size;
+returnmemory+1;
+}
+
+staticinlinevoid*
+pm_debug_calloc(size_tnmemb, size_tsize)
+{
+size_ttotal_size=nmemb*size;
+void*ptr=pm_debug_malloc(total_size);
+memset(ptr, 0, total_size);
+returnptr;
+}
+
+staticinlinevoid*
+pm_debug_realloc(void*ptr, size_tsize)
+{
+if (ptr==NULL) {
+returnpm_debug_malloc(size);
+ }
+
+size_t*memory= (size_t*)ptr;
+void*raw_memory=memory-1;
+memory= (size_t*)xrealloc(raw_memory, size+sizeof(size_t));
+memory[0] =size;
+returnmemory+1;
+}
+
+staticinlinevoid
+pm_debug_free(void*ptr)
+{
+if (ptr!=NULL) {
+size_t*memory= (size_t*)ptr;
+xfree(memory-1);
+ }
+}
+
+staticinlinevoid
+pm_debug_free_sized(void*ptr, size_told_size)
+{
+if (ptr!=NULL) {
+size_t*memory= (size_t*)ptr;
+if (old_size!=memory[-1]) {
+fprintf(stderr, "[BUG] buffer %p was allocated with size %lu but freed with size %lu\n", ptr, memory[-1], old_size);
+abort();
+ }
+xfree_sized(memory-1, old_size+sizeof(size_t));
+ }
+}
+
+staticinlinevoid*
+pm_debug_realloc_sized(void*ptr, size_tsize, size_told_size)
+{
+if (ptr==NULL) {
+if (old_size!=0) {
+fprintf(stderr, "[BUG] realloc_sized called with NULL pointer and old size %lu\n", old_size);
+abort();
+ }
+returnpm_debug_malloc(size);
+ }
+
+size_t*memory= (size_t*)ptr;
+if (old_size!=memory[-1]) {
+fprintf(stderr, "[BUG] buffer %p was allocated with size %lu but realloced with size %lu\n", ptr, memory[-1], old_size);
+abort();
+ }
+returnpm_debug_realloc(ptr, size);
+}
+
+#undef xmalloc
+#undef xrealloc
+#undef xcalloc
+#undef xfree
+#undef xrealloc_sized
+#undef xfree_sized
+
+#definexmalloc pm_debug_malloc
+#definexrealloc pm_debug_realloc
+#definexcalloc pm_debug_calloc
+#definexfree pm_debug_free
+#definexrealloc_sized pm_debug_realloc_sized
+#definexfree_sized pm_debug_free_sized
+
+#endif

include/prism/defines.h

@@ -161,10 +161,12 @@
  * ```
  * #ifndef PRISM_XALLOCATOR_H
  * #define PRISM_XALLOCATOR_H
- * #define xmalloc my_malloc
- * #define xrealloc my_realloc
- * #define xcalloc my_calloc
- * #define xfree my_free
+ * #define xmalloc my_malloc
+ * #define xrealloc my_realloc
+ * #define xcalloc my_calloc
+ * #define xfree my_free
+ * #define xrealloc_sized my_realloc_sized // (optional)
+ * #define xfree_sized my_free_sized // (optional)
  * #endif
  * ```
  */
@@ -204,6 +206,28 @@
 #endif
 #endif
 
+#ifndefxfree_sized
+/**
+ * The free_sized function that should be used. This can be overridden with the
+ * PRISM_XALLOCATOR define.
+ * If not defined, defaults to calling xfree.
+ */
+#definexfree_sized(p, s) xfree(((void)(s), (p)))
+#endif
+
+#ifndefxrealloc_sized
+/**
+ * The xrealloc_sized function that should be used. This can be overridden with the
+ * PRISM_XALLOCATOR define.
+ * If not defined, defaults to calling xrealloc.
+ */
+#definexrealloc_sized(p, ns, os) xrealloc((p), ((void)(os), (ns)))
+#endif
+
+#ifdefPRISM_BUILD_DEBUG
+#include"prism/debug_allocator.h"
+#endif
+
 /**
  * If PRISM_BUILD_MINIMAL is defined, then we're going to define every possible
  * switch that will turn off certain features of prism.

prism.gemspec

@@ -48,6 +48,7 @@ Gem::Specification.new do |spec|
 "ext/prism/extension.h",
 "include/prism.h",
 "include/prism/ast.h",
+"include/prism/debug_allocator.h",
 "include/prism/defines.h",
 "include/prism/diagnostic.h",
 "include/prism/encoding.h",

src/options.c

@@ -226,10 +226,10 @@ pm_options_free(pm_options_t *options) {
 pm_string_free(&scope->locals[local_index]);
  }
 
-xfree(scope->locals);
+xfree_sized(scope->locals, scope->locals_count*sizeof(pm_string_t));
  }
 
-xfree(options->scopes);
+xfree_sized(options->scopes, options->scopes_count*sizeof(pm_options_scope_t));
 }
 
 /**