From: Kurt Roeckx <kurt@roeckx.be>
Date: Tue, 22 Dec 2015 12:11:59 +0000 (+0100)
Subject: Avoid using a dangling pointer when removing the last item
X-Git-Tag: OpenSSL_1_1_0-pre2~167
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=933d10851640014142db0f3b02c2b740c2f0935f

Avoid using a dangling pointer when removing the last item

When it's the last item that is removed int_thread_hash == hash and we would
still call int_thread_release(&hash) while hash is already freed.  So
int_thread_release would compare that dangling pointer to NULL which is
undefined behaviour.  Instead do already what int_thread_release() would do,
and make the call do nothing instead.

Reviewed-by: Rich Salz <rsalz@openssl.org>

RT: #4155, MR: #1519
---

diff --git a/crypto/err/err.c b/crypto/err/err.c
index e487e980cb..9f81768ecc 100644
--- a/crypto/err/err.c
+++ b/crypto/err/err.c
@@ -399,8 +399,10 @@ static void int_thread_del_item(const ERR_STATE *d)
         if (int_thread_hash_references == 1
             && int_thread_hash
             && lh_ERR_STATE_num_items(int_thread_hash) == 0) {
+            int_thread_hash_references = 0;
             lh_ERR_STATE_free(int_thread_hash);
             int_thread_hash = NULL;
+            hash = NULL;
         }
     }
     CRYPTO_w_unlock(CRYPTO_LOCK_ERR);