drm/dp/mst: Validate REMOTE_I2C_READ harder
Make sure i2c msgs we're asked to transfer conform to the
requirements of REMOTE_I2C_READ. We were only checking that the
last message is a read, but we must also check that the preceding
messages are all writes. Also check that the length of each
message isn't too long.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180928180403.22499-2-ville.syrjala@linux.intel.com
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 229ad60..f0cbd5f 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3250,6 +3250,23 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);
+static bool remote_i2c_read_ok(const struct i2c_msg msgs[], int num)
+{
+ int i;
+
+ if (num - 1 > DP_REMOTE_I2C_READ_MAX_TRANSACTIONS)
+ return false;
+
+ for (i = 0; i < num - 1; i++) {
+ if (msgs[i].flags & I2C_M_RD ||
+ msgs[i].len > 0xff)
+ return false;
+ }
+
+ return msgs[num - 1].flags & I2C_M_RD &&
+ msgs[num - 1].len <= 0xff;
+}
+
/* I2C device */
static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
int num)
@@ -3259,7 +3276,6 @@ static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs
struct drm_dp_mst_branch *mstb;
struct drm_dp_mst_topology_mgr *mgr = port->mgr;
unsigned int i;
- bool reading = false;
struct drm_dp_sideband_msg_req_body msg;
struct drm_dp_sideband_msg_tx *txmsg = NULL;
int ret;
@@ -3268,12 +3284,7 @@ static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs
if (!mstb)
return -EREMOTEIO;
- /* construct i2c msg */
- /* see if last msg is a read */
- if (msgs[num - 1].flags & I2C_M_RD)
- reading = true;
-
- if (!reading || (num - 1 > DP_REMOTE_I2C_READ_MAX_TRANSACTIONS)) {
+ if (!remote_i2c_read_ok(msgs, num)) {
DRM_DEBUG_KMS("Unsupported I2C transaction for MST device\n");
ret = -EIO;
goto out;
