drm/amdkfd: validate SVM ioctl nattr against buffer size

drm/amdkfd: validate SVM ioctl nattr against buffer size

commit 045e0ff208f0838a246c10204105126611b267a1 upstream.

Validate nattr field against the buffer size, preventing
out-of-bounds buffer access via user-controlled attribute count.

Reviewed-by: Amir Shetaia <Amir.Shetaia@amd.com>
Signed-off-by: Alysa Liu <Alysa.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 5eca8bfdfa456c3304ca77523718fe24254c172f)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>