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SubjectRe: [PATCH] firmware: coreboot: Check size of table entry and split memcpy
Yeah, exactly. Isn't that a bit simpler? (I wasn't aware of the
flexible array member in union issue, but it sounds like we have a
neat solution for that already.)

On Fri, Jan 6, 2023 at 9:35 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Fri, Jan 06, 2023 at 04:03:35PM +0100, Julius Werner wrote:
> > Have you considered adding the flexible array member directly to the
> > union in struct coreboot_device instead? I think that would make this
> > a bit simpler by not having to copy header and data portion
> > separately.
>
> Are you thinking something like this?
>
>
> diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
> index 2652c396c423..564a3c908838 100644
> --- a/drivers/firmware/google/coreboot_table.c
> +++ b/drivers/firmware/google/coreboot_table.c
> @@ -93,14 +93,19 @@ static int coreboot_table_populate(struct device *dev, void *ptr)
> for (i = 0; i < header->table_entries; i++) {
> entry = ptr_entry;
>
> - device = kzalloc(sizeof(struct device) + entry->size, GFP_KERNEL);
> + if (entry->size < sizeof(*entry)) {
> + dev_warn(dev, "coreboot table entry too small!\n");
> + return -EINVAL;
> + }
> +
> + device = kzalloc(sizeof(device->dev) + entry->size, GFP_KERNEL);
> if (!device)
> return -ENOMEM;
>
> device->dev.parent = dev;
> device->dev.bus = &coreboot_bus_type;
> device->dev.release = coreboot_device_release;
> - memcpy(&device->entry, ptr_entry, entry->size);
> + memcpy(device->raw, entry, entry->size);
>
> switch (device->entry.tag) {
> case LB_TAG_CBMEM_ENTRY:
> diff --git a/drivers/firmware/google/coreboot_table.h b/drivers/firmware/google/coreboot_table.h
> index 37f4d335a606..d814dca33a08 100644
> --- a/drivers/firmware/google/coreboot_table.h
> +++ b/drivers/firmware/google/coreboot_table.h
> @@ -79,6 +79,7 @@ struct coreboot_device {
> struct lb_cbmem_ref cbmem_ref;
> struct lb_cbmem_entry cbmem_entry;
> struct lb_framebuffer framebuffer;
> + DECLARE_FLEX_ARRAY(u8, raw);
> };
> };
>
>
> --
> Kees Cook

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