_gnutls_buffer_resize: add option to use allocation simpler logic

This helps detect common mistakes[1] in realloc usage with valgrind,
where the caller assumes that the original ptr is always returned.

1. https://bugzilla.mozilla.org/show_bug.cgi?id=1377618

Signed-off-by: Daiki Ueno <ueno@gnu.org>
Co-authored-by: Alexander Sosedkin <asosedkin@redhat.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/lib/str.c b/lib/str.c
index 2247fc322b..506fe17210 100644
--- a/lib/str.c
+++ b/lib/str.c
@@ -138,6 +138,36 @@ gnutls_buffer_append_data(gnutls_buffer_t dest, const void *data,
 	return 0;
 }
 
+#ifdef AGGRESSIVE_REALLOC
+
+/* Use a simpler logic for reallocation; i.e., always call
+ * gnutls_realloc_fast() and do not reclaim the no-longer-used
+ * area which has been removed from the beginning of buffer
+ * with _gnutls_buffer_pop_datum().  This helps hit more
+ * issues when running under valgrind.
+ */
+int _gnutls_buffer_resize(gnutls_buffer_st * dest, size_t new_size)
+{
+	size_t unused;
+
+	if (unlikely(dest->data != NULL && dest->allocd == NULL))
+		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
+
+	unused = MEMSUB(dest->data, dest->allocd);
+	dest->allocd =
+	    gnutls_realloc_fast(dest->allocd, new_size);
+	if (dest->allocd == NULL) {
+		gnutls_assert();
+		return GNUTLS_E_MEMORY_ERROR;
+	}
+	dest->max_length = new_size;
+	dest->data = dest->allocd + unused;
+
+	return 0;
+}
+
+#else
+
 int _gnutls_buffer_resize(gnutls_buffer_st * dest, size_t new_size)
 {
 	if (unlikely(dest->data != NULL && dest->allocd == NULL))
@@ -171,6 +201,8 @@ int _gnutls_buffer_resize(gnutls_buffer_st * dest, size_t new_size)
 	}
 }
 
+#endif
+
 /* Appends the provided string. The null termination byte is appended
  * but not included in length.
  */