Re: [PATCH] virtio-console: avoid DMA from vmalloc area

[Arnd Bergmann]

On Tue, Jul 27, 2021 at 3:13 PM Xianting Tian
<xianting.tian@xxxxxxxxxxxxxxxxx> wrote:
> @@ -1127,13 +1128,18 @@ static int put_chars(u32 vtermno, const char *buf, int count)
>         if (!port)
>                 return -EPIPE;
>
> -       data = kmemdup(buf, count, GFP_ATOMIC);
> -       if (!data)
> -               return -ENOMEM;
> +       if (is_vmalloc_addr(buf)) {
> +               data = kmemdup(buf, count, GFP_ATOMIC);

What about buffers in .data? If those are in a loadable module, I guess you have
the same problem as with vmalloc() and vmap().

is_vmalloc_or_module_addr() would take care of both, not sure if there are
other examples that don't work. In theory it could be ioremap(), kmap_atomic()
or fixmap as well, but those seem less likely to matter here.

        Arnd