Avoid an unneccessary lock if we didn't add anything to the store

Partially fixes #20286

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20952)

1 files changed, 9 insertions, 5 deletions

diff --git a/crypto/x509/by_dir.c b/crypto/x509/by_dir.c
index 3c7f67b5a1..cd1b53740b 100644
--- a/crypto/x509/by_dir.c
+++ b/crypto/x509/by_dir.c
@@ -352,11 +352,15 @@ static int get_cert_by_subject_ex(X509_LOOKUP *xl, X509_LOOKUP_TYPE type,
          * Note: quadratic time find here since the objects won't generally be
          *       sorted and sorting the would result in O(n^2 log n) complexity.
          */
-        X509_STORE_lock(xl->store_ctx);
-        j = sk_X509_OBJECT_find(xl->store_ctx->objs, &stmp);
-        tmp = sk_X509_OBJECT_value(xl->store_ctx->objs, j);
-        X509_STORE_unlock(xl->store_ctx);
-
+        if (k > 0) {
+            X509_STORE_lock(xl->store_ctx);
+            j = sk_X509_OBJECT_find(xl->store_ctx->objs, &stmp);
+            tmp = sk_X509_OBJECT_value(xl->store_ctx->objs, j);
+            X509_STORE_unlock(xl->store_ctx);
+        } else {
+            j = -1;
+            tmp = NULL;
+        }
         /*
          * If a CRL, update the last file suffix added for this.
          * We don't need to add an entry if k is 0 as this is the initial value.