Re: [PATCH v3 04/11] gpu: nova-core: vbios: use checked access in `FwSecBiosImage::header`

["Alexandre Courbot" <acourbot@nvidia.com>]

On Tue Apr 21, 2026 at 5:20 PM JST, Eliot Courtney wrote:
> Use checked access in `FwSecBiosImage::header` for getting the header
> version since the value is firmware derived.
>
> Fixes: 47c4846e4319 ("gpu: nova-core: vbios: Add support for FWSEC ucode extraction")
> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
> ---
>  drivers/gpu/nova-core/vbios.rs | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index 632c8a90ea76..bc752d135cbf 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -996,17 +996,14 @@ fn build(self) -> Result<FwSecBiosImage> {
>  impl FwSecBiosImage {
>      /// Get the FwSec header ([`FalconUCodeDesc`]).
>      pub(crate) fn header(&self) -> Result<FalconUCodeDesc> {
> -        // Get the falcon ucode offset that was found in setup_falcon_data.
> -        let falcon_ucode_offset = self.falcon_ucode_offset;
> +        let data = self
> +            .base
> +            .data
> +            .get(self.falcon_ucode_offset..)
> +            .ok_or(EINVAL)?;
>  
> -        // Read the first 4 bytes to get the version.
> -        let hdr_bytes: [u8; 4] = self.base.data[falcon_ucode_offset..falcon_ucode_offset + 4]
> -            .try_into()
> -            .map_err(|_| EINVAL)?;
> -        let hdr = u32::from_le_bytes(hdr_bytes);
> -        let ver = (hdr & 0xff00) >> 8;
> -
> -        let data = self.base.data.get(falcon_ucode_offset..).ok_or(EINVAL)?;
> +        // Read the version byte from the header.
> +        let ver = data.get(1).copied().ok_or(EINVAL)?;

This doesn't need to be done with this patch, but once the kernel-wide
`bitfield` macro lands I hope we can use to to define a proper header
type for this and use it both here and in `firmware.rs` which does some
nasty bit masking - see for instance `FalconUCodeDescriptor::size`.