fix: stack-use-after-scope variable ordering (aws#4355)

Co-authored-by: Lindsay Stewart <stewart.r.lindsay@gmail.com>

tls/s2n_ktls_io.c

@@ -423,8 +423,9 @@ ssize_t s2n_ktls_sendv_with_offset(struct s2n_connection *conn, const struct iov
     POSIX_GUARD_RESULT(s2n_sendv_with_offset_total_size(bufs, count_in, offs_in, &total_bytes));
     POSIX_GUARD_RESULT(s2n_ktls_check_estimated_record_limit(conn, total_bytes));
 
-    DEFER_CLEANUP(struct s2n_blob new_bufs = { 0 }, s2n_free_or_wipe);
+    /* The order of new_bufs and new_bufs_mem matters. See https://github.com/aws/s2n-tls/issues/4354 */
     uint8_t new_bufs_mem[S2N_MAX_STACK_IOVECS_MEM] = { 0 };
+    DEFER_CLEANUP(struct s2n_blob new_bufs = { 0 }, s2n_free_or_wipe);
     POSIX_GUARD(s2n_blob_init(&new_bufs, new_bufs_mem, sizeof(new_bufs_mem)));
     if (offs > 0) {
         POSIX_GUARD_RESULT(s2n_ktls_update_bufs_with_offset(&bufs, &count, offs, &new_bufs));