sanity: Don't mark memory uninit in sanitize_{alloc,free}()

We might want to change the size of an allocated region without changing
which bytes are initialized.

3 files changed, 45 insertions, 19 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 79e4ce7..ef9f6ab 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -228,6 +228,7 @@ void arena_free(struct arena *arena, void *ptr) {
 	union chunk *chunk = ptr;
 	chunk_set_next(arena, chunk, arena->chunks);
 	arena->chunks = chunk;
+	sanitize_uninit(chunk, arena->size);
 	sanitize_free(chunk, arena->size);
 }
 
@@ -334,15 +335,16 @@ void *varena_realloc(struct varena *varena, void *ptr, size_t old_count, size_t
 	}
 
 	size_t old_size = old_arena->size;
-	sanitize_alloc((char *)ptr + old_exact_size, old_size - old_exact_size);
+	sanitize_alloc(ptr, old_size);
 
 	size_t new_size = new_arena->size;
 	size_t min_size = new_size < old_size ? new_size : old_size;
 	memcpy(ret, ptr, min_size);
 
 	arena_free(old_arena, ptr);
-	sanitize_free((char *)ret + new_exact_size, new_size - new_exact_size);
 
+	sanitize_free(ret, new_size);
+	sanitize_alloc(ret, new_exact_size);
 	return ret;
 }
 
diff --git a/src/sanity.h b/src/sanity.h
index 0b770cf..3f6020b 100644
--- a/src/sanity.h
+++ b/src/sanity.h
@@ -20,6 +20,11 @@
 #define SANITIZE_CALL__(macro, ptr, size, ...) \
 	macro(ptr, size)
 
+/**
+ * Squelch unused variable warnings when not sanitizing.
+ */
+#define sanitize_ignore(ptr, size) ((void)(ptr), (void)(size))
+
 #if __SANITIZE_ADDRESS__
 #  include <sanitizer/asan_interface.h>
 
@@ -38,8 +43,8 @@
 #define sanitize_free(...) SANITIZE_CALL(__asan_poison_memory_region, __VA_ARGS__)
 
 #else
-#  define sanitize_alloc sanitize_uninit
-#  define sanitize_free sanitize_uninit
+#  define sanitize_alloc(...) SANITIZE_CALL(sanitize_ignore, __VA_ARGS__)
+#  define sanitize_free(...) SANITIZE_CALL(sanitize_ignore, __VA_ARGS__)
 #endif
 
 #if __SANITIZE_MEMORY__
@@ -65,11 +70,6 @@
 #endif
 
 /**
- * Squelch unused variable warnings when not sanitizing.
- */
-#define sanitize_ignore(ptr, size) ((void)(ptr), (void)(size))
-
-/**
  * Initialize a variable, unless sanitizers would detect uninitialized uses.
  */
 #if __SANITIZE_MEMORY__
diff --git a/tests/alloc.c b/tests/alloc.c
index 5fc934b..4aae515 100644
--- a/tests/alloc.c
+++ b/tests/alloc.c
@@ -10,6 +10,27 @@
 #include <stdlib.h>
 #include <stdint.h>
 
+struct flexible {
+	alignas(64) int foo[8];
+	int bar[];
+};
+
+/** Check varena_realloc() poisoning for a size combination. */
+static struct flexible *check_varena_realloc(struct varena *varena, struct flexible *flexy, size_t old_count, size_t new_count) {
+	flexy = varena_realloc(varena, flexy, old_count, new_count);
+	bfs_everify(flexy);
+
+	for (size_t i = 0; i < new_count; ++i) {
+		if (i < old_count) {
+			bfs_check(flexy->bar[i] == (int)i);
+		} else {
+			flexy->bar[i] = i;
+		}
+	}
+
+	return flexy;
+}
+
 void check_alloc(void) {
 	// Check aligned allocation
 	void *ptr;
@@ -20,21 +41,14 @@ void check_alloc(void) {
 	free(ptr);
 
 	// Check sizeof_flex()
-	struct flexible {
-		alignas(64) int foo[8];
-		int bar[];
-	};
 	bfs_check(sizeof_flex(struct flexible, bar, 0) >= sizeof(struct flexible));
 	bfs_check(sizeof_flex(struct flexible, bar, 16) % alignof(struct flexible) == 0);
 
-	size_t too_many = SIZE_MAX / sizeof(int) + 1;
+	// volatile to suppress -Walloc-size-larger-than
+	volatile size_t too_many = SIZE_MAX / sizeof(int) + 1;
 	bfs_check(sizeof_flex(struct flexible, bar, too_many) == align_floor(alignof(struct flexible), SIZE_MAX));
 
 	// Make sure we detect allocation size overflows
-#if __GNUC__ && !__clang__
-#  pragma GCC diagnostic ignored "-Walloc-size-larger-than="
-#endif
-
 	bfs_check(ALLOC_ARRAY(int, too_many) == NULL && errno == EOVERFLOW);
 	bfs_check(ZALLOC_ARRAY(int, too_many) == NULL && errno == EOVERFLOW);
 	bfs_check(ALLOC_FLEX(struct flexible, bar, too_many) == NULL && errno == EOVERFLOW);
@@ -45,10 +59,20 @@ void check_alloc(void) {
 	VARENA_INIT(&varena, struct flexible, bar);
 
 	for (size_t i = 0; i < 256; ++i) {
-		bfs_verify(varena_alloc(&varena, i));
+		bfs_everify(varena_alloc(&varena, i));
 		struct arena *arena = &varena.arenas[varena.narenas - 1];
 		bfs_check(arena->size >= sizeof_flex(struct flexible, bar, i));
 	}
 
+	// Check varena_realloc() (un)poisoning
+	struct flexible *flexy = varena_alloc(&varena, 160);
+	bfs_everify(flexy);
+
+	flexy = check_varena_realloc(&varena, flexy, 0, 160);
+	flexy = check_varena_realloc(&varena, flexy, 160, 192);
+	flexy = check_varena_realloc(&varena, flexy, 192, 160);
+	flexy = check_varena_realloc(&varena, flexy, 160, 320);
+	flexy = check_varena_realloc(&varena, flexy, 320, 96);
+
 	varena_destroy(&varena);
 }