Libguestfs - May 2018 - [PATCH] common/qemuopts: ensure arg lists are never empty

Since it does not make much sense, then forbid this situation outright:
- change qemuopts_end_arg_list() to return an error if the current arg
  list has no elements
- when creating the argv array, assert that each arg list is not empty
---
 common/qemuopts/qemuopts.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/common/qemuopts/qemuopts.c b/common/qemuopts/qemuopts.c
index b3e69e306..49550bb21 100644
--- a/common/qemuopts/qemuopts.c
+++ b/common/qemuopts/qemuopts.c
@@ -453,7 +453,15 @@ qemuopts_append_arg_list_format (struct qemuopts *qopts,
 int
 qemuopts_end_arg_list (struct qemuopts *qopts)
 {
-  /* Nothing to do, the list is already well-formed. */
+  struct qopt *qopt;
+  size_t len;
+
+  qopt = last_option (qopts);
+  assert (qopt->type == QOPT_ARG_LIST);
+  len = count_strings (qopt->values);
+  if (len == 0)
+    return -1;
+
   return 0;
 }
 
@@ -816,7 +824,9 @@ qemuopts_to_argv (struct qemuopts *qopts)
     case QOPT_ARG_LIST:
       /* We only have to do comma-quoting here. */
       values = qopts->options[i].values;
-      len = count_strings (values) - 1 /* one for each comma */;
+      len = count_strings (values);
+      assert (len > 0);
+      len -= 1 /* one for each comma */;
       for (j = 0; values[j] != NULL; ++j) {
         for (k = 0; k < strlen (values[j]); ++k) {
           if (values[j][k] == ',') len++;
-- 
2.14.3

On Fri, May 04, 2018 at 03:55:36PM +0200, Pino Toscano
wrote:
> Since it does not make much sense, then forbid this situation outright:
> - change qemuopts_end_arg_list() to return an error if the current arg
>   list has no elements
> - when creating the argv array, assert that each arg list is not empty
> ---
>  common/qemuopts/qemuopts.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/common/qemuopts/qemuopts.c b/common/qemuopts/qemuopts.c
> index b3e69e306..49550bb21 100644
> --- a/common/qemuopts/qemuopts.c
> +++ b/common/qemuopts/qemuopts.c
> @@ -453,7 +453,15 @@ qemuopts_append_arg_list_format (struct qemuopts
*qopts,
>  int
>  qemuopts_end_arg_list (struct qemuopts *qopts)
>  {
> -  /* Nothing to do, the list is already well-formed. */
> +  struct qopt *qopt;
> +  size_t len;
> +
> +  qopt = last_option (qopts);
> +  assert (qopt->type == QOPT_ARG_LIST);
> +  len = count_strings (qopt->values);
> +  if (len == 0)
> +    return -1;
> +
>    return 0;
>  }
>  
> @@ -816,7 +824,9 @@ qemuopts_to_argv (struct qemuopts *qopts)
>      case QOPT_ARG_LIST:
>        /* We only have to do comma-quoting here. */
>        values = qopts->options[i].values;
> -      len = count_strings (values) - 1 /* one for each comma */;
> +      len = count_strings (values);
> +      assert (len > 0);
> +      len -= 1 /* one for each comma */;
>        for (j = 0; values[j] != NULL; ++j) {
>          for (k = 0; k < strlen (values[j]); ++k) {
>            if (values[j][k] == ',') len++;
> -- 
ACK

Rich.

-- 
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