tree e4ef565aaa999acea73d00a08e705fabde3b1920
parent 526b987888fbeb5c952912d41265156d53e9e849
author Nicolas Capens <capn@google.com> 1628888810 -0400
committer Nicolas Capens <nicolascapens@google.com> 1629125339 +0000

Fix integer overflow in vertex buffer access robustness check

The spec states that "vertex input attributes are considered out of
bounds if the offset of the attribute in the bound vertex buffer range
plus the size of the attribute is greater than ...". This addition can
cause integer overflow and make us fail to detect out of bounds
accesses.

Note there aren't x86 SIMD instructions for 32-bit arithmetic with
saturation. But we can cheaply prevent this overflow by first clamping
the offset to the range, and then doing the addition. Even for an
attribute size of 1, we would detect the out-of-bounds access.

Note that this relies on the range itself not being close to 4 GiB. We
currently limit all device memory allocations to 1 GiB, which ought to
be enough for anyone.

Bug: b/195684837
Bug: chromium:1234701
Change-Id: Ie8ec0859566e3aafb7a592bc4e92119a79016eb1
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/56271
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>