Fix possible leaks on sk_X509_EXTENSION_push() failure ...

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4677)

crypto/x509v3/v3_lib.c

@@ -54,6 +54,7 @@ const X509V3_EXT_METHOD *X509V3_EXT_get_nid(int nid)
     X509V3_EXT_METHOD tmp;
     const X509V3_EXT_METHOD *t = &tmp, *const *ret;
     int idx;
+
     if (nid < 0)
         return NULL;
     tmp.ext_nid = nid;
@@ -165,6 +166,7 @@ void *X509V3_get_d2i(const STACK_OF(X509_EXTENSION) *x, int nid, int *crit,
 {
     int lastpos, i;
     X509_EXTENSION *ex, *found_ex = NULL;
+
     if (!x) {
         if (idx)
             *idx = -1;
@@ -218,9 +220,9 @@ void *X509V3_get_d2i(const STACK_OF(X509_EXTENSION) *x, int nid, int *crit,
 int X509V3_add1_i2d(STACK_OF(X509_EXTENSION) **x, int nid, void *value,
                     int crit, unsigned long flags)
 {
-    int extidx = -1;
-    int errcode;
-    X509_EXTENSION *ext, *extmp;
+    int errcode, extidx = -1;
+    X509_EXTENSION *ext = NULL, *extmp;
+    STACK_OF(X509_EXTENSION) *ret = NULL;
     unsigned long ext_op = flags & X509V3_ADD_OP_MASK;
 
     /*
@@ -279,14 +281,23 @@ int X509V3_add1_i2d(STACK_OF(X509_EXTENSION) **x, int nid, void *value,
         return 1;
     }
 
+    ret = *x;
     if (*x == NULL
-        && (*x = sk_X509_EXTENSION_new_null()) == NULL)
-        return -1;
-    if (!sk_X509_EXTENSION_push(*x, ext))
-        return -1;
+        && (ret = sk_X509_EXTENSION_new_null()) == NULL)
+        goto m_fail;
+    if (!sk_X509_EXTENSION_push(ret, ext))
+        goto m_fail;
 
+    *x = ret;
     return 1;
 
+ m_fail:
+    /* X509V3err(X509V3_F_X509V3_ADD1_I2D, ERR_R_MALLOC_FAILURE); */
+    if (ret != *x)
+        sk_X509_EXTENSION_free(ret);
+    X509_EXTENSION_free(ext);
+    return -1;
+
  err:
     if (!(flags & X509V3_ADD_SILENT))
         X509V3err(X509V3_F_X509V3_ADD1_I2D, errcode);