qstring: Fix qstring_from_substr() not to provoke int overflow

qstring_from_substr() parameters @start and @end are of type int.
blkdebug_parse_filename(), blkverify_parse_filename(), nbd_parse_uri(),
and qstring_from_str() pass @end values of type size_t or ptrdiff_t.
Values exceeding INT_MAX get truncated, with possibly disastrous
results.

Such huge substrings seem unlikely, but we found one in a core dump,
where "info tlb" executed via QMP's human-monitor-command apparently
produced 35 GiB of output.

Fix by changing the parameters size_t.

Signed-off-by: liujunjie <liujunjie23@huawei.com>
Message-Id: <20180724134339.17832-1-liujunjie23@huawei.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/qobject/qstring.c b/qobject/qstring.c
index afca54b47a..18b8eb82f8 100644
--- a/qobject/qstring.c
+++ b/qobject/qstring.c
@@ -37,7 +37,7 @@ size_t qstring_get_length(const QString *qstring)
  *
  * Return string reference
  */
-QString *qstring_from_substr(const char *str, int start, int end)
+QString *qstring_from_substr(const char *str, size_t start, size_t end)
 {
     QString *qstring;