src/install: ensure invalidating slot status before updating

For the global slot status, RAUC kept the status information untouched
until a slot was actually fully written.
In most cases this is not a problem, except for when RAUC crashes
during a slot update and slot skipping (install-same=true) is enabled.
Then the respective slot might be broken but the status information
makes it look in good shape. Thus RAUC will skip it if the
to-be-installed checksum is equal to the one noted in the status file.
For this case, we would end up in an unusable installation.

Fix this by explicitly marking the status 'pending' and clearing the
checksum. This then also compatible with older RAUC installation (e.g.
in case of fallbacks) that can handle missing checksum an will thus not
erroneously assume a valid slot.

For the per-slot case this is not an issue since the status file is
stored on the slot and will thus be removed when updating the slot with
new content.

Signed-off-by: Enrico Joerns <ejo@pengutronix.de>

src/install.c

@@ -982,7 +982,7 @@ static gboolean handle_slot_install_plan(const RaucManifest *manifest, const RIm
 	load_slot_status(plan->target_slot);
 	slot_state = plan->target_slot->status;
 
-	/* In case we failed unmounting while reading status
+	/* In case we failed unmounting while reading per-slot status
 	 * file, abort here */
 	if (plan->target_slot->mount_point) {
 		g_set_error(error, R_INSTALL_ERROR, R_INSTALL_ERROR_MOUNTED,
@@ -991,6 +991,22 @@ static gboolean handle_slot_install_plan(const RaucManifest *manifest, const RIm
 		return FALSE;
 	}
 
+	/* For global slot status: Clear checksum info and make status
+	 * 'pending' to prevent the slot status from looking valid later in
+	 * case we crash while installing. */
+	if (g_strcmp0(r_context()->config->statusfile_path, "per-slot") != 0) {
+		g_clear_pointer(&slot_state->status, g_free);
+		slot_state->status = g_strdup("pending");
+		g_clear_pointer(&slot_state->checksum.digest, g_free);
+		slot_state->checksum.size = 0;
+
+		if (!save_slot_status(plan->target_slot, &ierror)) {
+			g_propagate_prefixed_error(error, ierror, "Error while writing status file: ");
+			r_context_end_step("check_slot", FALSE);
+			return FALSE;
+		}
+	}
+
 	/* if explicitly enabled, skip update of up-to-date slots */
 	if (!plan->target_slot->install_same && g_strcmp0(plan->image->checksum.digest, slot_state->checksum.digest) == 0) {
 		install_args_update(args, "Skipping update for correct image %s", plan->image->filename);