Quite a few of the ->diseqc_send_master_cmd() implementations don't
check cmd->msg_len so it can lead to memory corruption.

Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
---
I don't think it ever makes sense for ->msg_len to be longer than ->msg
but I am a newbie to this code.

diff --git a/drivers/media/dvb-core/dvb_frontend.c 
b/drivers/media/dvb-core/dvb_frontend.c
index a894d4c..aa6b48f 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -2403,7 +2403,13 @@ static int dvb_frontend_ioctl_legacy(struct file *file,
 
        case FE_DISEQC_SEND_MASTER_CMD:
                if (fe->ops.diseqc_send_master_cmd) {
-                       err = fe->ops.diseqc_send_master_cmd(fe, (struct 
dvb_diseqc_master_cmd*) parg);
+                       struct dvb_diseqc_master_cmd *cmd = parg;
+
+                       if (cmd->msg_len > sizeof(cmd->msg)) {
+                               err = -EINVAL;
+                               break;
+                       }
+                       err = fe->ops.diseqc_send_master_cmd(fe, cmd);
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
--
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