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From a436374994c47b12d5de1b8b1d191a098fa23594 Mon Sep 17 00:00:00 2001
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From: Nick Wellnhofer <wellnhofer@aevum.de>
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Date: Mon, 30 Jul 2018 12:54:38 +0200
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Subject: [PATCH] Fix nullptr deref with XPath logic ops
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If the XPath stack is corrupted, for example by a misbehaving extension
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function, the "and" and "or" XPath operators could dereference NULL
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pointers. Check that the XPath stack isn't empty and optimize the
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logic operators slightly.
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Closes: https://gitlab.gnome.org/GNOME/libxml2/issues/5
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Also see
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https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=901817
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https://bugzilla.redhat.com/show_bug.cgi?id=1595985
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This is CVE-2018-14404.
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Thanks to Guy Inbar for the report.
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---
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xpath.c | 10 ++++------
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1 file changed, 4 insertions(+), 6 deletions(-)
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diff --git a/xpath.c b/xpath.c
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index 3fae0bf4..5e3bb9ff 100644
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--- a/xpath.c
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+++ b/xpath.c
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@@ -13234,9 +13234,8 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
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return(0);
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}
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xmlXPathBooleanFunction(ctxt, 1);
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- arg1 = valuePop(ctxt);
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- arg1->boolval &= arg2->boolval;
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- valuePush(ctxt, arg1);
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+ if (ctxt->value != NULL)
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+ ctxt->value->boolval &= arg2->boolval;
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xmlXPathReleaseObject(ctxt->context, arg2);
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return (total);
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case XPATH_OP_OR:
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@@ -13252,9 +13251,8 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
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return(0);
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}
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xmlXPathBooleanFunction(ctxt, 1);
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- arg1 = valuePop(ctxt);
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- arg1->boolval |= arg2->boolval;
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- valuePush(ctxt, arg1);
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+ if (ctxt->value != NULL)
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+ ctxt->value->boolval |= arg2->boolval;
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xmlXPathReleaseObject(ctxt->context, arg2);
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return (total);
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case XPATH_OP_EQUAL:
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--
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2.22.0
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