[PATCH 4/5] gpu: nova-core: vbios: use checked access in `FwSecBiosImage::header`

[Eliot Courtney]

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")
Signed-off-by: Eliot Courtney <ecourtney@xxxxxxxxxx>
---
 drivers/gpu/nova-core/vbios.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index 2b0dc1a9125d..3bd3ac3a69f2 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -995,14 +995,16 @@ 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(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]
+        let hdr_bytes: [u8; 4] = data
+            .get(..4)
+            .ok_or(EINVAL)?
             .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)?;
         match ver {
             2 => {
                 let v2 = FalconUCodeDescV2::from_bytes_copy_prefix(data)

-- 
2.53.0