Commit 83ef843d92 for openssl.org

commit 83ef843d92ef8ffc953aca4d450e9fc586c470e9
Author: Bob Beck <beck@openssl.org>
Date:   Thu Apr 30 13:41:32 2026 -0600

    Guard memcmp for ub in X509_vpm.c

    Techincally unnecessary, since this thing won't let you add NULL
    data to it, but this is harmless and then obviously following
    the correct paradigm.

    Reviewed-by: Matt Caswell <matt@openssl.foundation>
    Reviewed-by: Eugene Syromiatnikov <esyr@openssl.org>
    MergeDate: Sat May  2 18:05:04 2026
    (Merged from https://github.com/openssl/openssl/pull/31049)

diff --git a/crypto/x509/x509_vpm.c b/crypto/x509/x509_vpm.c
index aa606f6320..bc2eb2cce1 100644
--- a/crypto/x509/x509_vpm.c
+++ b/crypto/x509/x509_vpm.c
@@ -110,6 +110,8 @@ static int buffer_cmp(const X509_BUFFER *const *a, const X509_BUFFER *const *b)
         return -1;
     if ((*a)->len > (*b)->len)
         return 1;
+    if ((*b)->len == 0)
+        return 0;
     return memcmp((*a)->data, (*b)->data, (*b)->len);
 }