[PATCH] media: rc: validate that "rc_proto" is reasonable

[Dan Carpenter <dan.carpenter@oracle.com>]

Smatch complains that "rc_proto" comes from the user and it can result
in shift wrapping in ir_raw_encode_scancode()

    drivers/media/rc/rc-ir-raw.c:526 ir_raw_encode_scancode()
    error: undefined (user controlled) shift '1 << protocol'

This is true, but I reviewed the surrounding code and it appears
harmless.  Anyway, let's verify that "rc_proto" is valid as a kernel
hardenning measure.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/media/rc/lirc_dev.c | 3 ++-
 include/uapi/linux/lirc.h   | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/lirc.h b/include/uapi/linux/lirc.h
index f99d9dcae667..c1eb960adde3 100644
--- a/include/uapi/linux/lirc.h
+++ b/include/uapi/linux/lirc.h
@@ -226,6 +226,7 @@ enum rc_proto {
 	RC_PROTO_RCMM24		= 25,
 	RC_PROTO_RCMM32		= 26,
 	RC_PROTO_XBOX_DVD	= 27,
+	RC_PROTO_MAX		= RC_PROTO_XBOX_DVD,
 };
 
 #endif
diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c
index 220363b9a868..116daf90c858 100644
--- a/drivers/media/rc/lirc_dev.c
+++ b/drivers/media/rc/lirc_dev.c
@@ -263,7 +263,8 @@ static ssize_t lirc_transmit(struct file *file, const char __user *buf,
 			goto out_unlock;
 		}
 
-		if (scan.flags || scan.keycode || scan.timestamp) {
+		if (scan.flags || scan.keycode || scan.timestamp ||
+		    scan.rc_proto > RC_PROTO_MAX) {
 			ret = -EINVAL;
 			goto out_unlock;
 		}
-- 
2.28.0