Re: [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*
From: Geert Uytterhoeven <hidden>
Date: 2018-12-14 09:54:47
Also in:
linux-iommu, lkml, sparclinux
Hi Christoph, On Fri, Dec 14, 2018 at 9:26 AM Christoph Hellwig [off-list ref] wrote:
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 hunk ↗ jump to hunk
--- 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?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org
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