[edk2-platforms][PATCH 1/1] Platform/RPi: Prevent buffer over-read when the command line is empty

["Pete Batard" <pete@akeo.ie>]

From: Andrei Warkentin <andrey.warkentin@gmail.com>

It is possible for the command line to be empty
(Cmd->TagHead.TagValueSize = 0), in which case the code should not
attempt to read the value at CommandLine[-1].

Signed-off-by: Pete Batard <pete@akeo.ie>
---
 Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.c b/Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.c
index 5a9d4c3f1787..9b4aa068857c 100644
--- a/Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.c
+++ b/Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.c
@@ -927,7 +927,8 @@ RpiFirmwareGetCommmandLine (
 
   CopyMem (CommandLine, Cmd->CommandLine, Cmd->TagHead.TagValueSize);
 
-  if (CommandLine[Cmd->TagHead.TagValueSize - 1] != '\0') {
+  if (Cmd->TagHead.TagValueSize == 0 ||
+      CommandLine[Cmd->TagHead.TagValueSize - 1] != '\0') {
     //
     // Add a NUL terminator if required.
     //
-- 
2.21.0.windows.1