terminal: verify kernel-returned DRM events are not truncated

Make sure the kernel always returns events properly. This is guaranteed
right now, otherwise, we do something really wrong. But lets be sure and
verify the received values properly. This also silences some coverity
warnings.

diff --git a/src/libsystemd-terminal/grdev-drm.c b/src/libsystemd-terminal/grdev-drm.c
index 5c65c096dec2cdfb736f0963698a06057ec01d3c..5393ebf98880c0ae1338e22e32958602f251d411 100644 (file)
--- a/src/libsystemd-terminal/grdev-drm.c
+++ b/src/libsystemd-terminal/grdev-drm.c
@@ -2223,7 +2223,7 @@ static int grdrm_card_io_fn(sd_event_source *s, int fd, uint32_t revents, void *
                 for (i = 0; i < l; i += event->length) {
                         event = (void*)&buf[i];
 
-                        if (i + event->length > l) {
+                        if (i + (ssize_t)sizeof(*event) > l || i + (ssize_t)event->length > l) {
                                 log_debug("grdrm: %s/%s: truncated event", card->base.session->name, card->base.name);
                                 break;
                         }