From 168636a9914ed01abc890d9e7e416c07af415d6a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 27 Nov 2014 11:12:59 -0500 Subject: [PATCH] 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. --- contrib/xml2/xslt_proc.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c index 6603526392d..5eb72b4a740 100644 --- a/contrib/xml2/xslt_proc.c +++ b/contrib/xml2/xslt_proc.c @@ -140,10 +140,10 @@ xslt_process(PG_FUNCTION_ARGS) if (xslt_sec_prefs_error) { + xsltFreeTransformContext(xslt_ctxt); + xsltFreeSecurityPrefs(xslt_sec_prefs); xsltFreeStylesheet(stylesheet); xmlFreeDoc(doctree); - xsltFreeSecurityPrefs(xslt_sec_prefs); - xsltFreeTransformContext(xslt_ctxt); xsltCleanupGlobals(); xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION, "could not set libxslt security preferences"); @@ -154,10 +154,10 @@ xslt_process(PG_FUNCTION_ARGS) if (restree == NULL) { + xsltFreeTransformContext(xslt_ctxt); + xsltFreeSecurityPrefs(xslt_sec_prefs); xsltFreeStylesheet(stylesheet); xmlFreeDoc(doctree); - xsltFreeSecurityPrefs(xslt_sec_prefs); - xsltFreeTransformContext(xslt_ctxt); xsltCleanupGlobals(); xml_ereport(ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION, "failed to apply stylesheet"); @@ -165,11 +165,11 @@ xslt_process(PG_FUNCTION_ARGS) resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet); - xsltFreeStylesheet(stylesheet); xmlFreeDoc(restree); - xmlFreeDoc(doctree); - xsltFreeSecurityPrefs(xslt_sec_prefs); xsltFreeTransformContext(xslt_ctxt); + xsltFreeSecurityPrefs(xslt_sec_prefs); + xsltFreeStylesheet(stylesheet); + xmlFreeDoc(doctree); xsltCleanupGlobals();