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

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

[Pete Batard]

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

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

[Philippe Mathieu-Daudé]

On 11/4/19 5:06 PM, 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].

Oops...

Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>

> 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.
>       //
> 

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

[Leif Lindholm]

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? Is there a more precise term for
this?

/
    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
> 

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

[Pete Batard]

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
>>

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

[Leif Lindholm]

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 :)

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?

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
> > > 
> 

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

[Pete Batard]

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
>>>>
>>

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

[Leif Lindholm]

On Thu, Nov 07, 2019 at 05:35:27PM +0000, Pete Batard wrote:
> 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.

Right. I meant something non-context-dependent. Nevermind :)

> > 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!

Done. And with that:
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Pushed as 92f06ccddfcf. 

Thanks!

/
    Leif

> /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
> > > > > 
> > > 
>