Add a missing error check for sk_X509_push

Change-Id: I4cf8af50d7355b447d3d7f9f92259febfc844b79
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/65127
Reviewed-by: Bob Beck <bbe@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/crypto/x509/x509_vfy.c b/crypto/x509/x509_vfy.c
index f64cfeb..4f6c4ad 100644
--- a/crypto/x509/x509_vfy.c
+++ b/crypto/x509/x509_vfy.c
@@ -400,7 +400,10 @@
       }
       ctx->current_cert = x;
     } else {
-      sk_X509_push(ctx->chain, chain_ss);
+      if (!sk_X509_push(ctx->chain, chain_ss)) {
+        ctx->error = X509_V_ERR_OUT_OF_MEM;
+        goto end;
+      }
       num++;
       ctx->last_untrusted = num;
       ctx->current_cert = chain_ss;