From e2e1fe5aad50809f00f6f5258432bd7aa605f47c Mon Sep 17 00:00:00 2001
From: Dean Camera <dean@fourwalledcubicle.com>
Date: Thu, 15 Jul 2010 04:45:31 +0000
Subject: [PATCH] Fixed possible buffer overrun in the XPLAINBridge project
 when in serial bridge mode.

---
 Projects/Benito/Lib/LightweightRingBuff.h     | 20 +++++++++++++++++++
 .../USBtoSerial/Lib/LightweightRingBuff.h     | 20 +++++++++++++++++++
 Projects/USBtoSerial/USBtoSerial.c            |  2 +-
 .../XPLAINBridge/Lib/LightweightRingBuff.h    | 20 +++++++++++++++++++
 Projects/XPLAINBridge/XPLAINBridge.c          |  2 +-
 5 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/Projects/Benito/Lib/LightweightRingBuff.h b/Projects/Benito/Lib/LightweightRingBuff.h
index 9c25707b41..0ffe792dcc 100644
--- a/Projects/Benito/Lib/LightweightRingBuff.h
+++ b/Projects/Benito/Lib/LightweightRingBuff.h
@@ -75,6 +75,26 @@
 			Buffer->Count = 0;
 		}
 		
+		/** Atomically determines if the specified ring buffer contains any free space. This should
+		 *  be tested before storing data to the buffer, to ensure that no data is lost due to a
+		 *  buffer overrun.
+		 *
+		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
+		 *
+		 *  \return Boolean true if the buffer contains no free space, false otherwise
+		 */		 
+		static inline bool RingBuffer_IsFull(RingBuff_t* const Buffer)
+		{
+			bool IsFull;
+			
+			ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+			{
+				IsFull = (Buffer->Count == BUFFER_SIZE);
+			}
+			
+			return IsFull;
+		}
+		
 		/** Atomically inserts an element into the ring buffer.
 		 *
 		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
diff --git a/Projects/USBtoSerial/Lib/LightweightRingBuff.h b/Projects/USBtoSerial/Lib/LightweightRingBuff.h
index 9c25707b41..0ffe792dcc 100644
--- a/Projects/USBtoSerial/Lib/LightweightRingBuff.h
+++ b/Projects/USBtoSerial/Lib/LightweightRingBuff.h
@@ -75,6 +75,26 @@
 			Buffer->Count = 0;
 		}
 		
+		/** Atomically determines if the specified ring buffer contains any free space. This should
+		 *  be tested before storing data to the buffer, to ensure that no data is lost due to a
+		 *  buffer overrun.
+		 *
+		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
+		 *
+		 *  \return Boolean true if the buffer contains no free space, false otherwise
+		 */		 
+		static inline bool RingBuffer_IsFull(RingBuff_t* const Buffer)
+		{
+			bool IsFull;
+			
+			ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+			{
+				IsFull = (Buffer->Count == BUFFER_SIZE);
+			}
+			
+			return IsFull;
+		}
+		
 		/** Atomically inserts an element into the ring buffer.
 		 *
 		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
diff --git a/Projects/USBtoSerial/USBtoSerial.c b/Projects/USBtoSerial/USBtoSerial.c
index 145047cbc4..1cd6f55634 100644
--- a/Projects/USBtoSerial/USBtoSerial.c
+++ b/Projects/USBtoSerial/USBtoSerial.c
@@ -84,7 +84,7 @@ int main(void)
 		/* Read bytes from the USB OUT endpoint into the USART transmit buffer */
 		for (uint8_t DataBytesRem = CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface); DataBytesRem != 0; DataBytesRem--)
 		{
-			if (!(BUFFER_SIZE - USBtoUSART_Buffer.Count))
+			if (RingBuffer_IsFull(&USBtoUSART_Buffer))
 			  break;
 			  
 			RingBuffer_AtomicInsert(&USBtoUSART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
diff --git a/Projects/XPLAINBridge/Lib/LightweightRingBuff.h b/Projects/XPLAINBridge/Lib/LightweightRingBuff.h
index 9c25707b41..0ffe792dcc 100644
--- a/Projects/XPLAINBridge/Lib/LightweightRingBuff.h
+++ b/Projects/XPLAINBridge/Lib/LightweightRingBuff.h
@@ -75,6 +75,26 @@
 			Buffer->Count = 0;
 		}
 		
+		/** Atomically determines if the specified ring buffer contains any free space. This should
+		 *  be tested before storing data to the buffer, to ensure that no data is lost due to a
+		 *  buffer overrun.
+		 *
+		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
+		 *
+		 *  \return Boolean true if the buffer contains no free space, false otherwise
+		 */		 
+		static inline bool RingBuffer_IsFull(RingBuff_t* const Buffer)
+		{
+			bool IsFull;
+			
+			ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+			{
+				IsFull = (Buffer->Count == BUFFER_SIZE);
+			}
+			
+			return IsFull;
+		}
+		
 		/** Atomically inserts an element into the ring buffer.
 		 *
 		 *  \param[in,out] Buffer  Pointer to a ring buffer structure to insert into
diff --git a/Projects/XPLAINBridge/XPLAINBridge.c b/Projects/XPLAINBridge/XPLAINBridge.c
index f08dfc5c78..3bbc0bc653 100644
--- a/Projects/XPLAINBridge/XPLAINBridge.c
+++ b/Projects/XPLAINBridge/XPLAINBridge.c
@@ -120,7 +120,7 @@ void UARTBridge_Task(void)
 	  return;
 
 	/* Read bytes from the USB OUT endpoint into the UART transmit buffer */
-	if (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface))
+	if (CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface) && !(RingBuffer_IsFull(&USBtoUART_Buffer)))
 	  RingBuffer_AtomicInsert(&USBtoUART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
 	
 	/* Check if the software UART flush timer has expired */