Re: [PATCH v3 2/4] gpu: nova-core: gsp: fix length of received messages

[Alexandre Courbot]

On Tue Dec 16, 2025 at 6:21 PM JST, Joel Fernandes wrote:
> Hi Alex,
>
>> On Dec 15, 2025, at 9:57 PM, Alexandre Courbot <acourbot@xxxxxxxxxx> wrote:
>> 
>> The size of messages' payload is miscalculated, leading to extra data
>> passed to the message handler. While this is not a problem with our
>> current set of commands, others with a variable-length payload may
>> misbehave. Fix this by introducing a method returning the payload size
>> and using it.
>> 
>> Fixes: 75f6b1de8133 ("gpu: nova-core: gsp: Add GSP command queue bindings and handling")
>> Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
>> Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
>> ---
>> drivers/gpu/nova-core/gsp/cmdq.rs | 10 ++++++----
>> drivers/gpu/nova-core/gsp/fw.rs   | 13 +++++++++----
>> 2 files changed, 15 insertions(+), 8 deletions(-)
>> 
>> diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
>> index 6f946d14868a..7985a0b3f769 100644
>> --- a/drivers/gpu/nova-core/gsp/cmdq.rs
>> +++ b/drivers/gpu/nova-core/gsp/cmdq.rs
>> @@ -588,21 +588,23 @@ fn wait_for_msg(&self, timeout: Delta) -> Result<GspMessage<'_>> {
>>             header.length(),
>>         );
>> 
>> +        let payload_length = header.payload_length();
>> +
>>         // Check that the driver read area is large enough for the message.
>> -        if slice_1.len() + slice_2.len() < header.length() {
>> +        if slice_1.len() + slice_2.len() < payload_length {
>>             return Err(EIO);
>>         }
>> 
>>         // Cut the message slices down to the actual length of the message.
>> -        let (slice_1, slice_2) = if slice_1.len() > header.length() {
>> +        let (slice_1, slice_2) = if slice_1.len() > payload_length {
>>             // PANIC: we checked above that `slice_1` is at least as long as `msg_header.length()`.
>> -            (slice_1.split_at(header.length()).0, &slice_2[0..0])
>> +            (slice_1.split_at(payload_length).0, &slice_2[0..0])
>>         } else {
>>             (
>>                 slice_1,
>>                 // PANIC: we checked above that `slice_1.len() + slice_2.len()` is at least as
>>                 // large as `msg_header.length()`.
>> -                slice_2.split_at(header.length() - slice_1.len()).0,
>> +                slice_2.split_at(payload_length - slice_1.len()).0,
>
> The panic comments also need updating?

Oh, they do - nice catch, thanks!