malloc-fail: Fix OOB read after xmlRegGetCounter

Found with libFuzzer, see #344.

(cherry picked from commit 1743c4c3fc58cf38ecce68db9de51d0f3651e033)

I also copied the error label from
e64653c0e7975594e27d7de2ed4be062c1e4ad03 to fix the build failure.

Bug: http://b/274231102
Test: TreeHugger
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:0e6ed17dfe8e36e5618a592a600720bd61e015cc)
Merged-In: I3bad3e03092e17a761cb6e299aff848ebd35b6f4
Change-Id: I3bad3e03092e17a761cb6e299aff848ebd35b6f4

xmlregexp.c

@@ -1673,6 +1673,8 @@ xmlFAGenerateTransitions(xmlRegParserCtxtPtr ctxt, xmlRegStatePtr from,
 			return(-1);
 		    inter = ctxt->state;
 		    counter = xmlRegGetCounter(ctxt);
+                    if (counter < 0)
+                        return(-1);
 		    ctxt->counters[counter].min = atom->min - 1;
 		    ctxt->counters[counter].max = atom->max - 1;
 		    /* count the number of times we see it again */
@@ -1691,6 +1693,8 @@ xmlFAGenerateTransitions(xmlRegParserCtxtPtr ctxt, xmlRegStatePtr from,
 		     * epsilon transition.
 		     */
 		    counter = xmlRegGetCounter(ctxt);
+                    if (counter < 0)
+                        return(-1);
 		    ctxt->counters[counter].min = atom->min - 1;
 		    ctxt->counters[counter].max = atom->max - 1;
 		    /* count the number of times we see it again */
@@ -6015,6 +6019,8 @@ xmlAutomataNewCountTrans2(xmlAutomataPtr am, xmlAutomataStatePtr from,
      * associate a counter to the transition.
      */
     counter = xmlRegGetCounter(am);
+    if (counter < 0)
+        goto error;
     am->counters[counter].min = min;
     am->counters[counter].max = max;
 
@@ -6034,6 +6040,10 @@ xmlAutomataNewCountTrans2(xmlAutomataPtr am, xmlAutomataStatePtr from,
     if (min == 0)
 	xmlFAGenerateEpsilonTransition(am, from, to);
     return(to);
+
+error:
+    xmlRegFreeAtom(atom);
+    return(NULL);
 }
 
 /**
@@ -6081,6 +6091,8 @@ xmlAutomataNewCountTrans(xmlAutomataPtr am, xmlAutomataStatePtr from,
      * associate a counter to the transition.
      */
     counter = xmlRegGetCounter(am);
+    if (counter < 0)
+        goto error;
     am->counters[counter].min = min;
     am->counters[counter].max = max;
 
@@ -6100,6 +6112,10 @@ xmlAutomataNewCountTrans(xmlAutomataPtr am, xmlAutomataStatePtr from,
     if (min == 0)
 	xmlFAGenerateEpsilonTransition(am, from, to);
     return(to);
+
+error:
+    xmlRegFreeAtom(atom);
+    return(NULL);
 }
 
 /**
@@ -6167,6 +6183,8 @@ xmlAutomataNewOnceTrans2(xmlAutomataPtr am, xmlAutomataStatePtr from,
      * associate a counter to the transition.
      */
     counter = xmlRegGetCounter(am);
+    if (counter < 0)
+        goto error;
     am->counters[counter].min = 1;
     am->counters[counter].max = 1;
 
@@ -6179,6 +6197,10 @@ xmlAutomataNewOnceTrans2(xmlAutomataPtr am, xmlAutomataStatePtr from,
     xmlRegAtomPush(am, atom);
     am->state = to;
     return(to);
+
+error:
+    xmlRegFreeAtom(atom);
+    return(NULL);
 }
 
 
@@ -6226,6 +6248,8 @@ xmlAutomataNewOnceTrans(xmlAutomataPtr am, xmlAutomataStatePtr from,
      * associate a counter to the transition.
      */
     counter = xmlRegGetCounter(am);
+    if (counter < 0)
+        goto error;
     am->counters[counter].min = 1;
     am->counters[counter].max = 1;
 
@@ -6238,6 +6262,10 @@ xmlAutomataNewOnceTrans(xmlAutomataPtr am, xmlAutomataStatePtr from,
     xmlRegAtomPush(am, atom);
     am->state = to;
     return(to);
+
+error:
+    xmlRegFreeAtom(atom);
+    return(NULL);
 }
 
 /**