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

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

Hi Leif,

On 2019.11.07 16:21, Leif Lindholm wrote:
> Patch looks good, but the term "command line" is a bit confusing.
> 
> I assume we're talking about whatever way parameters are passed from
> pre-edk2 firmware to edk2, right?

Yes. This is basically what the Raspberry Pi VideoCore bootcode digests 
and passes as boot arguments to the ARM boot loader (i.e. our TF-A + EFI 
firmware executable). It contains options that the user may have set in 
their 'config.txt' as well as other data.

> Is there a more precise term for this?

Would "boot arguments" or "external boot arguments" work for you? Or if 
you prefer "(external) boot parameters" should be applicable too.

Regards,

/Pete

> 
> /
>      Leif
> 
> On Mon, Nov 04, 2019 at 04:06:17PM +0000, Pete Batard wrote:
>> 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
>>