On Thu, Nov 16, 2023 at 12:54:59PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
> and should be replaced by flexible-array members. So, replace
> zero-length array with a flexible-array member in `struct
> privcmd_kernel_ioreq`.
>
> Also annotate array `ports` with `__counted_by()` to prepare for the
> coming implementation by GCC and Clang of the `__counted_by` attribute.
> Flexible array members annotated with `__counted_by` can have their
> accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
>
> This fixes multiple -Warray-bounds warnings:
> drivers/xen/privcmd.c:1239:30: warning: array subscript i is outside array
> bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1240:30: warning: array subscript i is outside array
> bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1241:30: warning: array subscript i is outside array
> bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1245:33: warning: array subscript i is outside array
> bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1258:67: warning: array subscript i is outside array
> bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>
> This results in no differences in binary output.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
Looks right to me. I can see the allocation:
size = struct_size(kioreq, ports, ioeventfd->vcpus);
kioreq = kzalloc(size, GFP_KERNEL);
if (!kioreq)
return ERR_PTR(-ENOMEM);
kioreq->dom = ioeventfd->dom;
kioreq->vcpus = ioeventfd->vcpus;
Reviewed-by: Kees Cook <keesc...@chromium.org>
--
Kees Cook
