Check return value of some BN functions.

Factorise multiple bn_get_top(group->field) calls
Add missing checks on some conditional BN_copy return value
Add missing checks on some BN_copy return value
Add missing checks on a few bn_wexpand return value

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1626)

1 files changed, 3 insertions, 2 deletions

diff --git a/crypto/bn/bn_mul.c b/crypto/bn/bn_mul.c
index 1ff8efe39c..4c39d404b5 100644
--- a/crypto/bn/bn_mul.c
+++ b/crypto/bn/bn_mul.c
@@ -970,8 +970,9 @@ int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
  end:
 #endif
     bn_correct_top(rr);
-    if (r != rr)
-        BN_copy(r, rr);
+    if (r != rr && BN_copy(r, rr) == NULL)
+        goto err;
+
     ret = 1;
  err:
     bn_check_top(r);