Free memory on error in PKCS7_dataFinal()

The PKCS7_dataFinal() function allocates a memory buffer but then fails
to free it on an error condition.

Reviewed-by: Richard Levitte <levitte@openssl.org>

crypto/pkcs7/pk7_doit.c

@@ -808,6 +808,7 @@ int PKCS7_dataFinal(PKCS7 *p7, BIO *bio)
                     goto err;
 
                 if (!EVP_SignFinal(ctx_tmp, abuf, &abuflen, si->pkey)) {
+                    OPENSSL_free(abuf);
                     PKCS7err(PKCS7_F_PKCS7_DATAFINAL, ERR_R_EVP_LIB);
                     goto err;
                 }