[PATCH 7/7] gpu: nova-core: falcon: check the per-block DMA offsets for overflow

[Alexandre Courbot <acourbot@nvidia.com>]

From: John Hubbard <jhubbard@nvidia.com>

Each block of a falcon DMA transfer is addressed by the start offset of
the transfer plus the block's position. The two additions were plain, so
a source or destination offset near the top of the 32-bit range would
have wrapped or panicked rather than failing the transfer.

Add the two with checked arithmetic and fail the transfer with EOVERFLOW
when a sum does not fit.

Assisted-by: LLM
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
[acourbot: split out of the DMA helper patch of v3.]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpu/nova-core/falcon.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/nova-core/falcon.rs b/drivers/gpu/nova-core/falcon.rs
index fb43d0ed2821..c54875e55da5 100644
--- a/drivers/gpu/nova-core/falcon.rs
+++ b/drivers/gpu/nova-core/falcon.rs
@@ -599,10 +599,11 @@ fn dma_wr(
             // Perform a transfer of size `DMA_LEN`.
             self.pfalcon.write_reg(
                 regs::NV_PFALCON_FALCON_DMATRFMOFFS::zeroed()
-                    .try_with_offs(load_offsets.dst_start + pos)?,
+                    .try_with_offs(load_offsets.dst_start.checked_add(pos).ok_or(EOVERFLOW)?)?,
             );
             self.pfalcon.write_reg(
-                regs::NV_PFALCON_FALCON_DMATRFFBOFFS::zeroed().with_offs(src_start + pos),
+                regs::NV_PFALCON_FALCON_DMATRFFBOFFS::zeroed()
+                    .with_offs(src_start.checked_add(pos).ok_or(EOVERFLOW)?),
             );
 
             self.pfalcon.write_reg(cmd);

-- 
2.56.0