sandbox: tpm: Tidy up reading and writing of device state

At present this code assumes that the TPM data has been read but this may
not be the case. Refactor the code to use a separate pointer so we know
the current state of the data.

Add error checking for the data size.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 24 insertions, 11 deletions

diff --git a/drivers/tpm/tpm_tis_sandbox.c b/drivers/tpm/tpm_tis_sandbox.c
index 294d98da60..f22ed846f0 100644
--- a/drivers/tpm/tpm_tis_sandbox.c
+++ b/drivers/tpm/tpm_tis_sandbox.c
@@ -20,7 +20,7 @@
 static struct tpm_state {
 	bool valid;
 	struct nvdata_state nvdata[NV_SEQ_COUNT];
-} g_state;
+} s_state, *g_state;
 
 /**
  * sandbox_tpm_read_state() - read the sandbox EC state from the state file
@@ -33,6 +33,7 @@ static struct tpm_state {
  */
 static int sandbox_tpm_read_state(const void *blob, int node)
 {
+	struct tpm_state *state = &s_state;
 	const char *prop;
 	int len;
 	int i;
@@ -41,22 +42,27 @@ static int sandbox_tpm_read_state(const void *blob, int node)
 		return 0;
 
 	for (i = 0; i < NV_SEQ_COUNT; i++) {
+		struct nvdata_state *nvd = &state->nvdata[i];
 		char prop_name[20];
 
 		sprintf(prop_name, "nvdata%d", i);
 		prop = fdt_getprop(blob, node, prop_name, &len);
-		if (prop && len == NV_DATA_SIZE) {
-			memcpy(g_state.nvdata[i].data, prop, NV_DATA_SIZE);
-			g_state.nvdata[i].present = true;
+		if (len >= NV_DATA_SIZE)
+			return log_msg_ret("nvd", -E2BIG);
+		if (prop) {
+			memcpy(nvd->data, prop, len);
+			nvd->length = len;
+			nvd->present = true;
 		}
 	}
-	g_state.valid = true;
+
+	s_state.valid = true;
 
 	return 0;
 }
 
 /**
- * cros_ec_write_state() - Write out our state to the state file
+ * sandbox_tpm_write_state() - Write out our state to the state file
  *
  * The caller will ensure that there is a node ready for the state. The node
  * may already contain the old state, in which case it is overridden.
@@ -66,20 +72,25 @@ static int sandbox_tpm_read_state(const void *blob, int node)
  */
 static int sandbox_tpm_write_state(void *blob, int node)
 {
+	const struct tpm_state *state = g_state;
 	int i;
 
+	if (!state)
+		return 0;
+
 	/*
 	 * We are guaranteed enough space to write basic properties.
 	 * We could use fdt_add_subnode() to put each set of data in its
 	 * own node - perhaps useful if we add access informaiton to each.
 	 */
 	for (i = 0; i < NV_SEQ_COUNT; i++) {
+		const struct nvdata_state *nvd = &state->nvdata[i];
 		char prop_name[20];
 
-		if (g_state.nvdata[i].present) {
-			sprintf(prop_name, "nvdata%d", i);
-			fdt_setprop(blob, node, prop_name,
-				    g_state.nvdata[i].data, NV_DATA_SIZE);
+		if (nvd->present) {
+			snprintf(prop_name, sizeof(prop_name), "nvdata%d", i);
+			fdt_setprop(blob, node, prop_name, nvd->data,
+				    nvd->length);
 		}
 	}
 
@@ -233,7 +244,9 @@ static int sandbox_tpm_probe(struct udevice *dev)
 {
 	struct tpm_state *tpm = dev_get_priv(dev);
 
-	memcpy(tpm, &g_state, sizeof(*tpm));
+	if (s_state.valid)
+		memcpy(tpm, &s_state, sizeof(*tpm));
+	g_state = tpm;
 
 	return 0;
 }