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>();
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
>
