On Tue, 19 Oct 2021, Christoph Hellwig wrote:
> We must never unencryped memory go back into the general page pool.
> So if we fail to set it back to encrypted when freeing DMA memory, leak
> the memory insted and warn the user.
>
> Signed-off-by: Christoph Hellwig <h...@lst.de>
> ---
> kernel/dma/direct.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 96f02248e7fa2..6673f7aebf787 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -264,9 +264,11 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> return ret;
>
> out_encrypt_pages:
> - /* If memory cannot be re-encrypted, it must be leaked */
> - if (dma_set_encrypted(dev, page_address(page), size))
> + if (dma_set_encrypted(dev, page_address(page), size)) {
> + pr_warn_ratelimited(
> + "leaking DMA memory that can't be re-encrypted\n");
> return NULL;
> + }
> out_free_pages:
> __dma_direct_free_pages(dev, page, size);
> return NULL;
> @@ -305,7 +307,11 @@ void dma_direct_free(struct device *dev, size_t size,
> dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
> return;
>
> - dma_set_encrypted(dev, cpu_addr, 1 << page_order);
> + if (dma_set_encrypted(dev, cpu_addr, 1 << page_order)) {
> + pr_warn_ratelimited(
> + "leaking DMA memory that can't be re-encrypted\n");
> + return;
> + }
>
> if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr))
> vunmap(cpu_addr);
> @@ -363,7 +369,10 @@ void dma_direct_free_pages(struct device *dev, size_t
> size,
> dma_free_from_pool(dev, vaddr, size))
> return;
>
> - dma_set_encrypted(dev, vaddr, 1 << page_order);
> + if (dma_set_encrypted(dev, vaddr, 1 << page_order)) {
> + pr_warn_ratelimited(
> + "leaking DMA memory that can't be re-encrypted\n");
> + }
Is this actually leaking the memory?
> __dma_direct_free_pages(dev, page, size);
> }
>
> --
> 2.30.2
>
>
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