Fix NULL pointer dereference in the ex_data code

In some circumstances the global data held in the "global" variable can
be NULL, so we should error out in the circumstance instead of crashing.

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/9035)

diff --git a/crypto/ex_data.c b/crypto/ex_data.c
index 055420a95df660be4ce5fb472fcfc04acf4d195c..d7d0d5a726b893710e51c3d0526a521900094e03 100644 (file)
--- a/crypto/ex_data.c
+++ b/crypto/ex_data.c
@@ -36,7 +36,7 @@ static EX_CALLBACKS *get_and_lock(OPENSSL_CTX *ctx, int class_index)
     }
 
     global = openssl_ctx_get_ex_data_global(ctx);
-    if (global->ex_data_lock == NULL) {
+    if (global == NULL || global->ex_data_lock == NULL) {
         /*
          * This can happen in normal operation when using CRYPTO_mem_leaks().
          * The CRYPTO_mem_leaks() function calls OPENSSL_cleanup() which cleans