On 2025-12-12 at 18:59 +1100, Joel Fernandes <[email protected]> wrote...
> Hi Alex,
>
> > On Nov 22, 2025, at 12:00 AM, Alexandre Courbot <[email protected]> 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.
> >
> > Signed-off-by: Alexandre Courbot <[email protected]>
> > ---
> > drivers/gpu/nova-core/gsp/cmdq.rs | 11 +++++++----
> > drivers/gpu/nova-core/gsp/fw.rs | 2 +-
> > 2 files changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs
> > b/drivers/gpu/nova-core/gsp/cmdq.rs
> > index 6f946d14868a..dab73377c526 100644
> > --- a/drivers/gpu/nova-core/gsp/cmdq.rs
> > +++ b/drivers/gpu/nova-core/gsp/cmdq.rs
> > @@ -588,21 +588,24 @@ fn wait_for_msg(&self, timeout: Delta) ->
> > Result<GspMessage<'_>> {
> > header.length(),
> > );
> >
> > + // The length of the message that follows the header.
> > + let msg_length = header.length() - size_of::<GspMsgElement>();
Wouldn't it be better to add a new method to GspMsgElement to get the size of
the associated message rather than open coding it here?
- Alistair
> Is this immune to under flow without one of the checked subtraction wrappers?
> Either way, we should not tolerate the underflow I think. Which means it can
> panic when the rust overflow checks are enabled. Since the header length
> comes from firmware, this cannot be guaranteed to not underflow in the event
> of a malformed message.
>
> thanks,
>
> - Joel
>
>
>
> > +
> > // 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() < msg_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() > msg_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(msg_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(msg_length - slice_1.len()).0,
> > )
> > };
> >
> > diff --git a/drivers/gpu/nova-core/gsp/fw.rs
> > b/drivers/gpu/nova-core/gsp/fw.rs
> > index abffd6beec65..7fcba5afb0a3 100644
> > --- a/drivers/gpu/nova-core/gsp/fw.rs
> > +++ b/drivers/gpu/nova-core/gsp/fw.rs
> > @@ -853,7 +853,7 @@ pub(crate) fn set_checksum(&mut self, checksum: u32) {
> > self.inner.checkSum = checksum;
> > }
> >
> > - /// Returns the total length of the message.
> > + /// Returns the total length of the message, message and RPC headers
> > included.
> > pub(crate) fn length(&self) -> usize {
> > // `rpc.length` includes the length of the GspRpcHeader but not the
> > message header.
> > size_of::<Self>() - size_of::<bindings::rpc_message_header_v>()
> >
> > --
> > 2.51.2
> >
