firmware: arm_scmi: Avoid using extended string-buffers sizes if not necessary

Commit b260fccaebdc2 ("firmware: arm_scmi: Add SCMI v3.1 protocol extended
names support") moved all the name string buffers to use the extended buffer
size of 64 instead of the required 16 bytes. While that should be fine if
the firmware terminates the string before 16 bytes, there is possibility
of copying random data if the name is not NULL terminated by the firmware.

SCMI base protocol agent_name/vendor_id/sub_vendor_id are defined by the
specification as NULL-terminated ASCII strings up to 16-bytes in length.

The underlying buffers and message descriptors are currently bigger than
needed; resize them to fit only the strictly needed 16 bytes to avoid
any possible leaks when reading data from the firmware.

Change the size argument of strlcpy to use SCMI_SHORT_NAME_MAX_SIZE always
when dealing with short domain names, so as to limit the possibility that
an ill-formed non-NULL terminated short reply from the SCMI platform
firmware can leak stale content laying in the underlying transport shared
memory area.

While at that, convert all strings handling routines to use the preferred
strscpy.

Link: https://lore.kernel.org/r/20220608095530.497879-1-cristian.marussi@arm.com
Fixes: b260fccaebdc2 ("firmware: arm_scmi: Add SCMI v3.1 protocol extended names support")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

9 files changed, 16 insertions, 17 deletions

diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c
index d0ac96da1ddf..a52f084a6a87 100644
--- a/drivers/firmware/arm_scmi/base.c
+++ b/drivers/firmware/arm_scmi/base.c
@@ -36,7 +36,7 @@ struct scmi_msg_resp_base_attributes {
 
 struct scmi_msg_resp_base_discover_agent {
 	__le32 agent_id;
-	u8 name[SCMI_MAX_STR_SIZE];
+	u8 name[SCMI_SHORT_NAME_MAX_SIZE];
 };
 
 
@@ -119,7 +119,7 @@ scmi_base_vendor_id_get(const struct scmi_protocol_handle *ph, bool sub_vendor)
 
 	ret = ph->xops->do_xfer(ph, t);
 	if (!ret)
-		memcpy(vendor_id, t->rx.buf, size);
+		strscpy(vendor_id, t->rx.buf, size);
 
 	ph->xops->xfer_put(ph, t);
 
@@ -276,7 +276,7 @@ static int scmi_base_discover_agent_get(const struct scmi_protocol_handle *ph,
 	ret = ph->xops->do_xfer(ph, t);
 	if (!ret) {
 		agent_info = t->rx.buf;
-		strlcpy(name, agent_info->name, SCMI_MAX_STR_SIZE);
+		strscpy(name, agent_info->name, SCMI_SHORT_NAME_MAX_SIZE);
 	}
 
 	ph->xops->xfer_put(ph, t);
@@ -375,7 +375,7 @@ static int scmi_base_protocol_init(const struct scmi_protocol_handle *ph)
 	int id, ret;
 	u8 *prot_imp;
 	u32 version;
-	char name[SCMI_MAX_STR_SIZE];
+	char name[SCMI_SHORT_NAME_MAX_SIZE];
 	struct device *dev = ph->dev;
 	struct scmi_revision_info *rev = scmi_revision_area_get(ph);
 
diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c
index 1a718faa4192..c7a83f6e38e5 100644
--- a/drivers/firmware/arm_scmi/clock.c
+++ b/drivers/firmware/arm_scmi/clock.c
@@ -153,7 +153,7 @@ static int scmi_clock_attributes_get(const struct scmi_protocol_handle *ph,
 	if (!ret) {
 		u32 latency = 0;
 		attributes = le32_to_cpu(attr->attributes);
-		strlcpy(clk->name, attr->name, SCMI_MAX_STR_SIZE);
+		strscpy(clk->name, attr->name, SCMI_SHORT_NAME_MAX_SIZE);
 		/* clock_enable_latency field is present only since SCMI v3.1 */
 		if (PROTOCOL_REV_MAJOR(version) >= 0x2)
 			latency = le32_to_cpu(attr->clock_enable_latency);
diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
index c1f701623058..bbb0331801ff 100644
--- a/drivers/firmware/arm_scmi/perf.c
+++ b/drivers/firmware/arm_scmi/perf.c
@@ -252,7 +252,7 @@ scmi_perf_domain_attributes_get(const struct scmi_protocol_handle *ph,
 			dom_info->mult_factor =
 					(dom_info->sustained_freq_khz * 1000) /
 					dom_info->sustained_perf_level;
-		strlcpy(dom_info->name, attr->name, SCMI_MAX_STR_SIZE);
+		strscpy(dom_info->name, attr->name, SCMI_SHORT_NAME_MAX_SIZE);
 	}
 
 	ph->xops->xfer_put(ph, t);
diff --git a/drivers/firmware/arm_scmi/power.c b/drivers/firmware/arm_scmi/power.c
index 964882cc8747..356e83631664 100644
--- a/drivers/firmware/arm_scmi/power.c
+++ b/drivers/firmware/arm_scmi/power.c
@@ -122,7 +122,7 @@ scmi_power_domain_attributes_get(const struct scmi_protocol_handle *ph,
 		dom_info->state_set_notify = SUPPORTS_STATE_SET_NOTIFY(flags);
 		dom_info->state_set_async = SUPPORTS_STATE_SET_ASYNC(flags);
 		dom_info->state_set_sync = SUPPORTS_STATE_SET_SYNC(flags);
-		strlcpy(dom_info->name, attr->name, SCMI_MAX_STR_SIZE);
+		strscpy(dom_info->name, attr->name, SCMI_SHORT_NAME_MAX_SIZE);
 	}
 	ph->xops->xfer_put(ph, t);
 
diff --git a/drivers/firmware/arm_scmi/protocols.h b/drivers/firmware/arm_scmi/protocols.h
index 73304af5ec4a..c679f3fb8718 100644
--- a/drivers/firmware/arm_scmi/protocols.h
+++ b/drivers/firmware/arm_scmi/protocols.h
@@ -24,8 +24,6 @@
 
 #include <asm/unaligned.h>
 
-#define SCMI_SHORT_NAME_MAX_SIZE	16
-
 #define PROTOCOL_REV_MINOR_MASK	GENMASK(15, 0)
 #define PROTOCOL_REV_MAJOR_MASK	GENMASK(31, 16)
 #define PROTOCOL_REV_MAJOR(x)	((u16)(FIELD_GET(PROTOCOL_REV_MAJOR_MASK, (x))))
diff --git a/drivers/firmware/arm_scmi/reset.c b/drivers/firmware/arm_scmi/reset.c
index a420a9102094..673f3eb498f4 100644
--- a/drivers/firmware/arm_scmi/reset.c
+++ b/drivers/firmware/arm_scmi/reset.c
@@ -116,7 +116,7 @@ scmi_reset_domain_attributes_get(const struct scmi_protocol_handle *ph,
 		dom_info->latency_us = le32_to_cpu(attr->latency);
 		if (dom_info->latency_us == U32_MAX)
 			dom_info->latency_us = 0;
-		strlcpy(dom_info->name, attr->name, SCMI_MAX_STR_SIZE);
+		strscpy(dom_info->name, attr->name, SCMI_SHORT_NAME_MAX_SIZE);
 	}
 
 	ph->xops->xfer_put(ph, t);
diff --git a/drivers/firmware/arm_scmi/sensors.c b/drivers/firmware/arm_scmi/sensors.c
index 8a93dd944c49..7288c6117838 100644
--- a/drivers/firmware/arm_scmi/sensors.c
+++ b/drivers/firmware/arm_scmi/sensors.c
@@ -412,7 +412,7 @@ iter_axes_desc_process_response(const struct scmi_protocol_handle *ph,
 	attrh = le32_to_cpu(adesc->attributes_high);
 	a->scale = S32_EXT(SENSOR_SCALE(attrh));
 	a->type = SENSOR_TYPE(attrh);
-	strscpy(a->name, adesc->name, SCMI_MAX_STR_SIZE);
+	strscpy(a->name, adesc->name, SCMI_SHORT_NAME_MAX_SIZE);
 
 	if (a->extended_attrs) {
 		unsigned int ares = le32_to_cpu(adesc->resolution);
@@ -634,7 +634,7 @@ iter_sens_descr_process_response(const struct scmi_protocol_handle *ph,
 			    SUPPORTS_AXIS(attrh) ?
 			    SENSOR_AXIS_NUMBER(attrh) : 0,
 			    SCMI_MAX_NUM_SENSOR_AXIS);
-	strscpy(s->name, sdesc->name, SCMI_MAX_STR_SIZE);
+	strscpy(s->name, sdesc->name, SCMI_SHORT_NAME_MAX_SIZE);
 
 	/*
 	 * If supported overwrite short name with the extended
diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
index 97df6d3dd131..5de93f637bd4 100644
--- a/drivers/firmware/arm_scmi/voltage.c
+++ b/drivers/firmware/arm_scmi/voltage.c
@@ -233,7 +233,7 @@ static int scmi_voltage_descriptors_get(const struct scmi_protocol_handle *ph,
 		v = vinfo->domains + dom;
 		v->id = dom;
 		attributes = le32_to_cpu(resp_dom->attr);
-		strlcpy(v->name, resp_dom->name, SCMI_MAX_STR_SIZE);
+		strscpy(v->name, resp_dom->name, SCMI_SHORT_NAME_MAX_SIZE);
 
 		/*
 		 * If supported overwrite short name with the extended one;
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 1c58646ba381..704111f63993 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -13,8 +13,9 @@
 #include <linux/notifier.h>
 #include <linux/types.h>
 
-#define SCMI_MAX_STR_SIZE	64
-#define SCMI_MAX_NUM_RATES	16
+#define SCMI_MAX_STR_SIZE		64
+#define SCMI_SHORT_NAME_MAX_SIZE	16
+#define SCMI_MAX_NUM_RATES		16
 
 /**
  * struct scmi_revision_info - version information structure
@@ -36,8 +37,8 @@ struct scmi_revision_info {
 	u8 num_protocols;
 	u8 num_agents;
 	u32 impl_ver;
-	char vendor_id[SCMI_MAX_STR_SIZE];
-	char sub_vendor_id[SCMI_MAX_STR_SIZE];
+	char vendor_id[SCMI_SHORT_NAME_MAX_SIZE];
+	char sub_vendor_id[SCMI_SHORT_NAME_MAX_SIZE];
 };
 
 struct scmi_clock_info {