Re: [PATCH v2] qga-win: Free GMatchInfo properly

[Konstantin Kostiuk]

On Thu, Jun 10, 2021 at 7:02 PM Daniel P. Berrangé <berrange@redhat.com> wrote:

On Thu, Jun 10, 2021 at 06:58:11PM +0300, Kostiantyn Kostiuk wrote:
> The g_regex_match function creates match_info even if it
> returns FALSE. So we should always call g_match_info_free.
> A better solution is using g_autoptr for match_info variable.
>
> Signed-off-by: Kostiantyn Kostiuk <konstantin@daynix.com>
> ---
>  qga/commands-win32.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> index 300b87c859..785a5cc6b2 100644
> --- a/qga/commands-win32.c
> +++ b/qga/commands-win32.c
> @@ -2494,7 +2494,7 @@ GuestDeviceInfoList *qmp_guest_get_devices(Error **errp)
>              continue;
>          }
>          for (j = 0; hw_ids[j] != NULL; j++) {
> -            GMatchInfo *match_info;
> +            g_autoptr(GMatchInfo) match_info;

This should be initialized to NULL otherwise...

>              GuestDeviceIdPCI *id;
>              if (!g_regex_match(device_pci_re, hw_ids[j], 0, &match_info)) {
>                  continue;

this continue will trigger freeing of unintialized memory

But we always call match_info, so match_info is always initialized.

The g_regex_match function creates match_info even if it returns FALSE.

 

Essentially all g_auto* variables should be init to NULL
at all times, even if it currently looks harmless.

> @@ -2511,7 +2511,6 @@ GuestDeviceInfoList *qmp_guest_get_devices(Error **errp)
>              id->vendor_id = g_ascii_strtoull(vendor_id, NULL, 16);
>              id->device_id = g_ascii_strtoull(device_id, NULL, 16);
> 
> -            g_match_info_free(match_info);
>              break;
>          }
>          if (skip) {

Regards,
Daniel
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Best wishes,

Kostiantyn Kostiuk