Re: [PATCH 1/2] util/virxml: use xmlCtxtGetLastError when applicable

[Michal Prívozník <mprivozn@xxxxxxxxxx>]

On 9/11/24 15:37, Jakub Palacky wrote:
> xmlParserCtxt->lastError was deprecated in libxml2 v2.13.0-103-g1228b4e0
> xmlCtxtGetLastError(xmlParserCtxt) should be used instead
> 
> Signed-off-by: Jakub Palacky <jpalacky@xxxxxxxxxx>
> ---
>  src/util/virxml.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/src/util/virxml.c b/src/util/virxml.c
> index a7b75fd7b3..b72b63f55f 100644
> --- a/src/util/virxml.c
> +++ b/src/util/virxml.c
> @@ -1035,8 +1035,8 @@ catchXMLError(void *ctx, const char *msg G_GNUC_UNUSED, ...)
>      if (!ctxt ||
>          (virGetLastErrorCode()) ||
>          ctxt->input == NULL ||
> -        ctxt->lastError.level != XML_ERR_FATAL ||
> -        ctxt->lastError.message == NULL)
> +        xmlCtxtGetLastError(ctxt)->level != XML_ERR_FATAL ||
> +        xmlCtxtGetLastError(ctxt)->message == NULL)

Looking at xmlCtxtGetLastError() it can return NULL. From parseInternals.c:

const xmlError *
xmlCtxtGetLastError(void *ctx)
{
    xmlParserCtxtPtr ctxt = (xmlParserCtxtPtr) ctx;

    if (ctxt == NULL)
        return (NULL);
    if (ctxt->lastError.code == XML_ERR_OK)
        return (NULL);
    return (&ctxt->lastError);
}


Now, ctxt == NULL is checked for by us, so that shouldn't happen. But
ctxt->lasterror.code == XML_ERR_OK could happen, though - this is in a
callback function that's supposed to be called when an error occurred.
Nevertheless, I'd feel a bit safer if xmlCtxtGetLastError()'s retval was
checked for before dereferencing it.

Michal