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Free libxml2/libxslt resources in a safer order. 

Mark Simonetti reported that libxslt sometimes crashes for him, and that
swapping xslt_process's object-freeing calls around to do them in reverse
order of creation seemed to fix it.  I've not reproduced the crash, but
valgrind clearly shows a reference to already-freed memory, which is
consistent with the idea that shutdown of the xsltTransformContext is
trying to reference the already-freed stylesheet or input document.
With this patch, valgrind is no longer unhappy.

I have an inquiry in to see if this is a libxslt bug or if we're just
abusing the library; but even if it's a library bug, we'd want to adjust
our code so it doesn't fail with unpatched libraries.

Back-patch to all supported branches, because we've been doing this in
the wrong(?) order for a long time.
This commit is contained in:
Tom Lane 2014-11-27 11:12:55 -05:00
parent 9b468bcec1
commit a1cd04cd0d
1 changed files with 9 additions and 9 deletions
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18
contrib/xml2/xslt_proc.c
View File

@ -150,16 +150,16 @@ xslt_process(PG_FUNCTION_ARGS)
} }
PG_CATCH(); PG_CATCH();
{ {
if (stylesheet != NULL)
xsltFreeStylesheet(stylesheet);
if (restree != NULL) if (restree != NULL)
xmlFreeDoc(restree); xmlFreeDoc(restree);
if (doctree != NULL)
xmlFreeDoc(doctree);
if (xslt_sec_prefs != NULL)
xsltFreeSecurityPrefs(xslt_sec_prefs);
if (xslt_ctxt != NULL) if (xslt_ctxt != NULL)
xsltFreeTransformContext(xslt_ctxt); xsltFreeTransformContext(xslt_ctxt);
if (xslt_sec_prefs != NULL)
xsltFreeSecurityPrefs(xslt_sec_prefs);
if (stylesheet != NULL)
xsltFreeStylesheet(stylesheet);
if (doctree != NULL)
xmlFreeDoc(doctree);
xsltCleanupGlobals(); xsltCleanupGlobals();
pg_xml_done(xmlerrcxt, true); pg_xml_done(xmlerrcxt, true);
@ -168,11 +168,11 @@ xslt_process(PG_FUNCTION_ARGS)
} }
PG_END_TRY(); PG_END_TRY();
xsltFreeStylesheet(stylesheet);
xmlFreeDoc(restree); xmlFreeDoc(restree);
xmlFreeDoc(doctree);
xsltFreeSecurityPrefs(xslt_sec_prefs);
xsltFreeTransformContext(xslt_ctxt); xsltFreeTransformContext(xslt_ctxt);
xsltFreeSecurityPrefs(xslt_sec_prefs);
xsltFreeStylesheet(stylesheet);
xmlFreeDoc(doctree);
xsltCleanupGlobals(); xsltCleanupGlobals();
pg_xml_done(xmlerrcxt, false); pg_xml_done(xmlerrcxt, false);