Re: [PATCH v1 2/5] gpu: nova-core: use checked arithmetic in Booter signature parsing

[Zhi Wang]

On Sat, 24 Jan 2026 18:18:27 -0500
Joel Fernandes <joelagnelf@xxxxxxxxxx> wrote:

> Use checked_add() when computing signature offsets from firmware-
> provided values in signatures_iter().
> 
> Without checked arithmetic, overflow could wrap to a small plausible
> offset that points to entirely wrong data.
> 
> Signed-off-by: Joel Fernandes <joelagnelf@xxxxxxxxxx>
> ---
>  drivers/gpu/nova-core/firmware/booter.rs | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/firmware/booter.rs
> b/drivers/gpu/nova-core/firmware/booter.rs index
> 86556cee8e67..f5ad619dc055 100644 ---
> a/drivers/gpu/nova-core/firmware/booter.rs +++
> b/drivers/gpu/nova-core/firmware/booter.rs @@ -119,14 +119,23 @@ fn
> signatures_iter(&'a self) -> Result<impl Iterator<Item =
> BooterSignature<'a>> Some(sig_size) => { let patch_sig =
>                      frombytes_at::<u32>(self.fw,
> self.hdr.patch_sig_offset.into_safe_cast())?;
> -                let signatures_start =
> usize::from_safe_cast(self.hdr.sig_prod_offset + patch_sig); +
> +                // Compute signatures_start = hdr.sig_prod_offset +
> patch_sig.
> +                let signatures_start = self
> +                    .hdr
> +                    .sig_prod_offset
> +                    .checked_add(patch_sig)
> +                    .map(usize::from_safe_cast)
> +                    .ok_or(EINVAL)?;
> +
> +                // Compute signatures_end = signatures_start +
> hdr.sig_prod_size.
> +                let signatures_end = signatures_start
> +
> .checked_add(usize::from_safe_cast(self.hdr.sig_prod_size))
> +                    .ok_or(EINVAL)?;
>  

The same concern of comment format in PATCH 1 raised by Dirk, With that
addressed,

Reviewed-by: Zhi Wang <zhiw@xxxxxxxxxx>

>                  self.fw
>                      // Get signatures range.
> -                    .get(
> -                        signatures_start
> -                            ..signatures_start +
> usize::from_safe_cast(self.hdr.sig_prod_size),
> -                    )
> +                    .get(signatures_start..signatures_end)
>                      .ok_or(EINVAL)?
>                      .chunks_exact(sig_size.into_safe_cast())
>              }