From 4736eab947b470a5b6522da2c8f6bf485e363e52 Mon Sep 17 00:00:00 2001
From: Andy Polyakov <appro@openssl.org>
Date: Thu, 29 Mar 2012 21:35:28 +0000
Subject: [PATCH] bn/bn_gf2m.c: make new BN_GF2m_mod_inv work with
 BN_DEBUG_RAND.

---
 crypto/bn/bn_gf2m.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/crypto/bn/bn_gf2m.c b/crypto/bn/bn_gf2m.c
index 0bfb56971e..e54a701166 100644
--- a/crypto/bn/bn_gf2m.c
+++ b/crypto/bn/bn_gf2m.c
@@ -631,8 +631,11 @@ int BN_GF2m_mod_inv(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
 			}
 		if (ubits==vbits)
 			{
-			bn_correct_top(u);
-			ubits = BN_num_bits(u);
+			BN_ULONG u;
+			int utop = (ubits-1)/BN_BITS2;
+
+			while ((u=udp[utop])==0 && utop) utop--;
+			ubits = utop*BN_BITS2 + BN_num_bits_word(u);
 			}
 		}
 	bn_correct_top(b);
-- 
2.25.1