On 11/16/23 15:08, Kees Cook wrote:
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 <[email protected]>
Looks right to me. I can see the allocation:
Yep, I always check for that; in particular, the 'counter' assignment. :)
Do you want me to mention it in the changelog text?
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 <[email protected]>
Thanks!
--
Gustavo
