Re: [PATCH] dma-buf: explicitely forbid exposing pages from get_user_pages()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Misspelling of the word 'explicitly' as 'explicitely' in both the commit message and the newly added source code comments. Additionally, 'import mechanism' is slightly awkward grammatically and would read better as 'import mechanisms'.
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commit d403e672a4ce196480792c8a6cdd1c4a2ffcf542
Author: Christian König <ckoenig.leichtzumerken@gmail.com>

dma-buf: explicitely forbid exposing pages from get_user_pages()

This commit documents that DMA-buf exporters are forbidden from exposing
pages they do not own, such as those acquired by get_user_pages(). It also
discourages exposing the same backing store through multiple DMA-bufs to
avoid aliasing and cache coherency problems.

> dma-buf: explicitely forbid exposing pages from get_user_pages()

[Severity: Low]
This isn't a bug, but there is a typo (explicitely) in the subject line.

> Explicitely document that this is not something exporters can do.

[Severity: Low]
This isn't a bug, but there is a typo (Explicitely) in the commit message.

> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index d504c636dc294..b2efc3085e6d6 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -685,6 +685,14 @@ static struct file *dma_buf_getfile(size_t size, int flags)
>   *
>   * For the detailed semantics exporters are expected to implement see
>   * &dma_buf_ops.
> + *
> + * It is explicitely forbidden for exporters to expose buffers they don't "own"
> + * as DMA-buf. This includes pages acquired by get_user_pages() or other import
> + * mechanism. Not following this rule can create numerous security problems.

[Severity: Low]
This isn't a bug, but there is a typo (explicitely) in the new comment.
Additionally, would it read better to use the plural "mechanisms" here
instead of "mechanism"?

> + *
> + * It is also strongly discouraged to expose the same backing store through
> + * multiple DMA-bufs at the same time. This eventually creates aliasing and
> + * cache coherency problems which are extremely hard to debug and fix.
>   */

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Sashiko AI review · https://sashiko.dev/#/patchset/20260630080112.1117341-1-christian.koenig@amd.com?part=1