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I think it would be a good idea to send this up to https://github.com/masoncl/review-prompts/blob/main/kernel/subsystem/drm.md as well. That's what Sashiko uses and it will help flag this in case it happens in future. > > Signed-off-by: Christian König > --- > drivers/dma-buf/dma-buf.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index 71f37544a5c6..aa5af4f439c2 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. > + * > + * 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. > */ > > /**