Re: [PATCH 1/5] gpu: nova-core: vbios: fix various cases of reading past `BIOS_MAX_SCAN_LEN`

Joel Fernandes
2026-04-10T14:08:58Z

On 4/10/2026 4:38 AM, Eliot Courtney wrote:
> Fix various cases that allow reading past `BIOS_MAX_SCAN_LEN` when
> scanning the VBIOS.
>
> Fix bug where `read_more_at_offset` would unnecessarily read more data.
> This happens when the window to read has some part cached and some part
> not. It would read `len` bytes instead of just the uncached portion,
> which could read past `BIOS_MAX_SCAN_LEN`.
>
> Also add more checked arithmetic to catch potential overflows.
> `read_bios_image_at_offset` is called with a length from the VBIOS
> header, so we should be more defensive here.
>
> Fixes: 6fda04e7f0cd ("gpu: nova-core: vbios: Add base support for VBIOS construction and iteration")
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
> ---
> drivers/gpu/nova-core/vbios.rs | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index ebda28e596c5..6de7e58e0da0 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -132,17 +132,14 @@ fn read_more(&mut self, len: usize) -> Result {
>
> /// Read bytes at a specific offset, filling any gap.
> fn read_more_at_offset(&mut self, offset: usize, len: usize) -> Result {
> - if offset > BIOS_MAX_SCAN_LEN {
> + let end = offset.checked_add(len).ok_or(EINVAL)?;
> +
> + if end > BIOS_MAX_SCAN_LEN {
> dev_err!(self.dev, "Error: exceeded BIOS scan limit.\n");
> return Err(EINVAL);
> }
>
> - // If `offset` is beyond current data size, fill the gap first.
> - let current_len = self.data.len();
> - let gap_bytes = offset.saturating_sub(current_len);
> -
> - // Now read the requested bytes at the offset.
> - self.read_more(gap_bytes + len)
> + self.read_more(end.saturating_sub(self.data.len()))
> }
>
> /// Read a BIOS image at a specific offset and create a [`BiosImage`] from it.
> @@ -155,8 +152,9 @@ fn read_bios_image_at_offset(
> len: usize,
> context: &str,
> ) -> Result<BiosImage> {
> + let end = offset.checked_add(len).ok_or(EINVAL)?;
> let data_len = self.data.len();
> - if offset + len > data_len {
> + if end > data_len {
> self.read_more_at_offset(offset, len).inspect_err(|e| {
> dev_err!(
> self.dev,
> @@ -167,7 +165,7 @@ fn read_bios_image_at_offset(
> })?;
> }
>
> - BiosImage::new(self.dev, &self.data[offset..offset + len]).inspect_err(|err| {
> + BiosImage::new(self.dev, &self.data[offset..end]).inspect_err(|err| {
> dev_err!(
> self.dev,
> "Failed to {} at offset {:#x}: {:?}\n",
> @@ -189,7 +187,7 @@ fn next(&mut self) -> Option<Self::Item> {
> return None;
> }
>
> - if self.current_offset > BIOS_MAX_SCAN_LEN {
> + if self.current_offset >= BIOS_MAX_SCAN_LEN {
> dev_err!(self.dev, "Error: exceeded BIOS scan limit, stopping scan\n");
> return None;
> }
Very nice!

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

thanks,

--
Joel Fernandes