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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 11:13:03 -05:00
parent 9880fea4fd
commit 6a694bbab2
1 changed files with 7 additions and 7 deletions
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14
contrib/xml2/xslt_proc.c
View File

@ -139,10 +139,10 @@ 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");
@ -153,10 +153,10 @@ 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");
@ -164,11 +164,11 @@ 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();