Re: [Qemu-devel] [PATCH] qstring: Fix qstring_from_substr() not to provoke int overflow

[Markus Armbruster]

liujunjie <address@hidden> writes:

> 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 <address@hidden>
> ---
>  include/qapi/qmp/qstring.h | 2 +-
>  qobject/qstring.c          | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h
> index b3b3d44..3e83e3a 100644
> --- a/include/qapi/qmp/qstring.h
> +++ b/include/qapi/qmp/qstring.h
> @@ -24,7 +24,7 @@ struct QString {
>  
>  QString *qstring_new(void);
>  QString *qstring_from_str(const char *str);
> -QString *qstring_from_substr(const char *str, int start, int end);
> +QString *qstring_from_substr(const char *str, size_t start, size_t end);
>  size_t qstring_get_length(const QString *qstring);
>  const char *qstring_get_str(const QString *qstring);
>  const char *qstring_get_try_str(const QString *qstring);
> diff --git a/qobject/qstring.c b/qobject/qstring.c
> index afca54b..18b8eb8 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;

Reviewed-by: Markus Armbruster <address@hidden>