libknot: rework knot_map_errno and keep just one variant

The previous knot_map_errno was vulnerable to stack buffer undeflow
if the input list was not terminated with a zero.

src/libknot/errcode.c

@@ -14,15 +14,12 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <stdarg.h>
 #include <stdio.h>
-#include <stdlib.h>
 #if HAVE_LMDB
 #include <lmdb.h>
 #endif
 
 #include "libknot/errcode.h"
-#include "libknot/internal/errcode.h"
 #include "libknot/internal/macros.h"
 #include "dnssec/error.h"
 
@@ -189,15 +186,3 @@ const char *knot_strerror(int code)
 
 	return fallback_message(code);
 }
-
-_public_
-int knot_map_errno(int arg0, ...)
-{
-	/* Iterate all variable-length arguments. */
-	va_list ap;
-	va_start(ap, arg0);
-	int ret = knot_map_errno_internal(KNOT_ERROR, arg0, ap);
-	va_end(ap);
-
-	return ret;
-}

src/libknot/errcode.h

@@ -27,7 +27,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #pragma once
 
-#include <errno.h>
 #include "libknot/internal/errcode.h"
 
 /*!
@@ -39,11 +38,4 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 const char *knot_strerror(int code);
 
-/*!
- * \brief Map POSIX errno to Knot error code.
- *
- * KNOT_ERROR is used as a fallback error, the list is terminated implicitly.
- */
-int knot_map_errno(int arg0, ...);
-
 /*! @} */

src/libknot/internal/errcode.c

@@ -14,35 +14,46 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <stdarg.h>
-#include <stdio.h>
-#include <stdlib.h>
-#if HAVE_LMDB
-#include <lmdb.h>
-#endif
-
 #include "libknot/internal/errcode.h"
 #include "libknot/internal/macros.h"
 
+#define ERR_ITEM(name) { name, KNOT_##name }
+
+typedef struct {
+	int errno_code;
+	int libknot_code;
+} err_table_t;
+
+/*!
+ * \brief Errno to libknot error mapping table.
+ */
+static const err_table_t errno_to_errcode[] = {
+	ERR_ITEM(ENOMEM),
+	ERR_ITEM(EINVAL),
+	ERR_ITEM(ENOTSUP),
+	ERR_ITEM(EBUSY),
+	ERR_ITEM(EAGAIN),
+	ERR_ITEM(EACCES),
+	ERR_ITEM(ECONNREFUSED),
+	ERR_ITEM(EISCONN),
+	ERR_ITEM(EADDRINUSE),
+	ERR_ITEM(ENOENT),
+	ERR_ITEM(EEXIST),
+	ERR_ITEM(ERANGE),
+	ERR_ITEM(EADDRNOTAVAIL),
+
+	/* Terminator - default value. */
+	{ 0, KNOT_ERROR }
+};
+
 _public_
-int knot_map_errno_internal(int fallback, int arg0, ...)
+int knot_map_errno(void)
 {
-	/* Iterate all variable-length arguments. */
-	va_list ap;
-	va_start(ap, arg0);
-
-	/* KNOT_ERROR serves as a sentinel. */
-	for (int c = arg0; c != 0; c = va_arg(ap, int)) {
-
-		/* Error code matches with mapped. */
-		if (c == errno) {
-			/* Return negative value of the code. */
-			va_end(ap);
-			return -abs(c);
-		}
+	const err_table_t *err = errno_to_errcode;
+
+	while (err->errno_code != 0 && err->errno_code != errno) {
+		err++;
 	}
-	va_end(ap);
 
-	/* Fallback error code. */
-	return KNOT_ERROR;
+	return err->libknot_code;
 }

src/libknot/internal/errcode.h

@@ -145,13 +145,8 @@ enum knot_error {
 /*!
  * \brief Get a POSIX errno mapped to Knot error code.
  *
- * \internal
- *
- * \param fallback  Falback error code.
- * \param arg0...   Error codes allowed for lookup, list must be terminated by 0.
- *
- * \return Mapped errno or fallback error code.
+ * \return Mapped errno or KNOT_ERROR if unknown.
  */
-int knot_map_errno_internal(int fallback, int arg0, ...);
+int knot_map_errno(void);
 
 /*! @} */