[PATCH v3 10/26] media: lirc: validate scancode for transmit

[Sean Young <sean@xxxxxxxx>]

Ensure we reject an attempt to transmit invalid scancodes.

Signed-off-by: Sean Young <sean@xxxxxxxx>
---
 drivers/media/rc/ir-lirc-codec.c | 10 ++++++++
 drivers/media/rc/rc-core-priv.h  |  1 +
 drivers/media/rc/rc-main.c       | 53 +++++++++++++++++++++++++---------------
 3 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/drivers/media/rc/ir-lirc-codec.c b/drivers/media/rc/ir-lirc-codec.c
index f2feca17c3a0..d9406fdbc9a3 100644
--- a/drivers/media/rc/ir-lirc-codec.c
+++ b/drivers/media/rc/ir-lirc-codec.c
@@ -121,6 +121,16 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char __user *buf,
 		if (scan.flags || scan.keycode || scan.timestamp)
 			return -EINVAL;
 
+		/*
+		 * The scancode field in lirc_scancode is 64-bit simply
+		 * to future-proof it, since there are IR protocols encode
+		 * use more than 32 bits. For now only 32-bit protocols
+		 * are supported.
+		 */
+		if (scan.scancode > U32_MAX ||
+		    !rc_validate_scancode(scan.rc_proto, scan.scancode))
+			return -EINVAL;
+
 		if (dev->tx_scancode) {
 			ret = dev->tx_scancode(dev, &scan);
 			return ret < 0 ? ret : n;
diff --git a/drivers/media/rc/rc-core-priv.h b/drivers/media/rc/rc-core-priv.h
index 21e515d34f64..a064c401fa38 100644
--- a/drivers/media/rc/rc-core-priv.h
+++ b/drivers/media/rc/rc-core-priv.h
@@ -160,6 +160,7 @@ static inline bool is_timing_event(struct ir_raw_event ev)
 #define TO_STR(is_pulse)		((is_pulse) ? "pulse" : "space")
 
 /* functions for IR encoders */
+bool rc_validate_scancode(enum rc_proto proto, u32 scancode);
 
 static inline void init_ir_raw_event_duration(struct ir_raw_event *ev,
 					      unsigned int pulse,
diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index 758c14b90a87..38393f13822f 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -776,6 +776,37 @@ void rc_keydown_notimeout(struct rc_dev *dev, enum rc_proto protocol,
 EXPORT_SYMBOL_GPL(rc_keydown_notimeout);
 
 /**
+ * rc_validate_scancode() - checks that a scancode is valid for a protocol
+ * @proto:	protocol
+ * @scancode:	scancode
+ */
+bool rc_validate_scancode(enum rc_proto proto, u32 scancode)
+{
+	switch (proto) {
+	case RC_PROTO_NECX:
+		if ((((scancode >> 16) ^ ~(scancode >> 8)) & 0xff) == 0)
+			return false;
+		break;
+	case RC_PROTO_NEC32:
+		if ((((scancode >> 24) ^ ~(scancode >> 16)) & 0xff) == 0)
+			return false;
+		break;
+	case RC_PROTO_RC6_MCE:
+		if ((scancode & 0xffff0000) != 0x800f0000)
+			return false;
+		break;
+	case RC_PROTO_RC6_6A_32:
+		if ((scancode & 0xffff0000) == 0x800f0000)
+			return false;
+		break;
+	default:
+		break;
+	}
+
+	return true;
+}
+
+/**
  * rc_validate_filter() - checks that the scancode and mask are valid and
  *			  provides sensible defaults
  * @dev:	the struct rc_dev descriptor of the device
@@ -793,26 +824,8 @@ static int rc_validate_filter(struct rc_dev *dev,
 
 	mask = protocols[protocol].scancode_bits;
 
-	switch (protocol) {
-	case RC_PROTO_NECX:
-		if ((((s >> 16) ^ ~(s >> 8)) & 0xff) == 0)
-			return -EINVAL;
-		break;
-	case RC_PROTO_NEC32:
-		if ((((s >> 24) ^ ~(s >> 16)) & 0xff) == 0)
-			return -EINVAL;
-		break;
-	case RC_PROTO_RC6_MCE:
-		if ((s & 0xffff0000) != 0x800f0000)
-			return -EINVAL;
-		break;
-	case RC_PROTO_RC6_6A_32:
-		if ((s & 0xffff0000) == 0x800f0000)
-			return -EINVAL;
-		break;
-	default:
-		break;
-	}
+	if (!rc_validate_scancode(protocol, s))
+		return -EINVAL;
 
 	filter->data &= mask;
 	filter->mask &= mask;
-- 
2.13.6