bio_mem: avoid pointer arithmetic on NULL

Prompted by a diff by Kenjiro Nakayama

ok jsing

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/libcrypto/bio/bss_mem.c b/src/lib/libcrypto/bio/bss_mem.c
index 3e4c1e2e3f..472863be43 100644
--- a/src/lib/libcrypto/bio/bss_mem.c
+++ b/src/lib/libcrypto/bio/bss_mem.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bss_mem.c,v 1.23 2025/05/10 05:54:38 tb Exp $ */
+/* $OpenBSD: bss_mem.c,v 1.24 2025/05/18 06:38:11 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -283,7 +283,9 @@ mem_ctrl(BIO *bio, int cmd, long num, void *ptr)
         case BIO_CTRL_INFO:
                 if (ptr != NULL) {
                         pptr = (void **)ptr;
-                        *pptr = bio_mem_read_ptr(bm);
+                        *pptr = NULL;
+                        if (bm->buf->max > 0)
+                                *pptr = bio_mem_read_ptr(bm);
                 }
                 ret = (long)bio_mem_pending(bm);
                 break;