On Fri, Dec 14, 2018 at 10:54 AM Geert Uytterhoeven
[off-list ref] wrote:

On Fri, Dec 14, 2018 at 9:26 AM Christoph Hellwig [off-list ref] wrote:

quoted

If we want to map memory from the DMA allocator to userspace it must be
zeroed at allocation time to prevent stale data leaks.   We already do
this on most common architectures, but some architectures don't do this
yet, fix them up, either by passing GFP_ZERO when we use the normal page
allocator or doing a manual memset otherwise.

Signed-off-by: Christoph Hellwig <redacted>

Thanks for your patch!

quoted

--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c

@@ -32,7 +32,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
        size = PAGE_ALIGN(size);
        order = get_order(size);

-       page = alloc_pages(flag, order);
+       page = alloc_pages(flag | GFP_ZERO, order);
        if (!page)
                return NULL;

There's second implementation below, which calls __get_free_pages() and
does an explicit memset().  As __get_free_pages() calls alloc_pages(), perhaps
it makes sense to replace the memset() by GFP_ZERO, to increase consistency?

Regardless, for m68k:
Acked-by: Geert Uytterhoeven <redacted>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds