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

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Message-ID: <63086256-CAD9-43AE-87CA-9569E6F392B1@nvidia.com>
Date: Tue, 16 Dec 2025 09:21:13 +0000
From: Joel Fernandes <joelagnelf@...dia.com>
To: Alexandre Courbot <acourbot@...dia.com>
CC: Danilo Krummrich <dakr@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Miguel
 Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng
	<boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, Benno Lossin
	<lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross
	<tmgross@...ch.edu>, John Hubbard <jhubbard@...dia.com>, Alistair Popple
	<apopple@...dia.com>, Timur Tabi <ttabi@...dia.com>, Edwin Peer
	<epeer@...dia.com>, "nouveau@...ts.freedesktop.org"
	<nouveau@...ts.freedesktop.org>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "rust-for-linux@...r.kernel.org"
	<rust-for-linux@...r.kernel.org>, Lyude Paul <lyude@...hat.com>, Alexandre
 Courbot <acourbot@...dia.com>
Subject: Re: [PATCH v3 2/4] gpu: nova-core: gsp: fix length of received
 messages

Hi Alex,

> On Dec 15, 2025, at 9:57 PM, Alexandre Courbot <acourbot@...dia.com> 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@...hat.com>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
> 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?

Other than the nit,

Reviewed-by: Joel Fernandes <joelagnelf@...dia.com>

thanks,

 - Joel



>             )
>         };
> 
> diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
> index abffd6beec65..7b8e710b33e7 100644
> --- a/drivers/gpu/nova-core/gsp/fw.rs
> +++ b/drivers/gpu/nova-core/gsp/fw.rs
> @@ -853,11 +853,16 @@ pub(crate) fn set_checksum(&mut self, checksum: u32) {
>         self.inner.checkSum = checksum;
>     }
> 
> -    /// Returns the total length of the message.
> +    /// Returns the length of the message's payload.
> +    pub(crate) fn payload_length(&self) -> usize {
> +        // `rpc.length` includes the length of the RPC message header.
> +        num::u32_as_usize(self.inner.rpc.length)
> +            .saturating_sub(size_of::<bindings::rpc_message_header_v>())
> +    }
> +
> +    /// 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>()
> -            + num::u32_as_usize(self.inner.rpc.length)
> +        size_of::<Self>() + self.payload_length()
>     }
> 
>     // Returns the sequence number of the message.
> 
> --
> 2.52.0
>