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

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

On 2019.11.07 17:27, Leif Lindholm wrote:
> On Thu, Nov 07, 2019 at 05:05:20PM +0000, Pete Batard wrote:
>> 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.
> 
> Sure.
> 
>>> 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.
> 
> Either would be fine - I was just hoping there might be a recognized
> standard name for them :)

Well, as far as I know, the recognized standard name is "commandline" as 
per 
https://www.raspberrypi.org/documentation/configuration/config-txt/boot.md

For instance there exists an option called disable_commandline_tags 
which pertains to what we are talking about.

> So, I could update the subject line to
> Platform/RPi: Prevent external boot arguments over-read
> in order to keep it short, and change "command line" in the commit
> message body to "external boot arguments" - does that work for you?

If you can do that, that's great. Thanks!

/Pete

> 
> Regards,
> 
> Leif
> 
>> 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
>>>>
>>