On Thu, Nov 05, 2020 at 02:48:05PM -0800, Jianxin Xiong wrote:
> + /* modify the sgl in-place to match umem address and length */
> +
> + start = ALIGN_DOWN(umem_dmabuf->umem.address, PAGE_SIZE);
> + end = ALIGN(umem_dmabuf->umem.address + umem_dmabuf->umem.length,
> + PAGE_SIZE);
> + cur = 0;
> + nmap = 0;
> + for_each_sgtable_dma_sg(sgt, sg, i) {
> + if (cur >= end)
> + break;
> + if (cur + sg_dma_len(sg) <= start) {
> + cur += sg_dma_len(sg);
> + continue;
> + }
This seems like a strange way to compute interesections
if (cur <= start && start < cur + sg_dma_len(sg))
> + if (cur <= start) {
> + unsigned long offset = start - cur;
> +
> + umem_dmabuf->first_sg = sg;
> + umem_dmabuf->first_sg_offset = offset;
> + sg_dma_address(sg) += offset;
> + sg_dma_len(sg) -= offset;
> + if (&sg_dma_len(sg) != &sg->length)
> + sg->length -= offset;
We don't need to adjust sg->length, only dma_len, so no reason for
this surprising if.
> + cur += offset;
> + }
> + if (cur + sg_dma_len(sg) >= end) {
Same logic here
> + unsigned long trim = cur + sg_dma_len(sg) - end;
> +
> + umem_dmabuf->last_sg = sg;
> + umem_dmabuf->last_sg_trim = trim;
> + sg_dma_len(sg) -= trim;
> + if (&sg_dma_len(sg) != &sg->length)
> + sg->length -= trim;
break, things are done here
> + }
> + cur += sg_dma_len(sg);
> + nmap++;
> + }
> +
> + umem_dmabuf->umem.sg_head.sgl = umem_dmabuf->first_sg;
> + umem_dmabuf->umem.sg_head.nents = nmap;
> + umem_dmabuf->umem.nmap = nmap;
> + umem_dmabuf->sgt = sgt;
> +
> + page_size = ib_umem_find_best_pgsz(&umem_dmabuf->umem, PAGE_SIZE,
> + umem_dmabuf->umem.iova);
> +
> + if (WARN_ON(cur != end || page_size != PAGE_SIZE)) {
Looks like nothing prevents this warn on to tigger
The user could specify a length that is beyond
the dma buf, can the dma buf length be checked during get?
Also page_size can be 0 because iova is not OK. iova should be checked
for alignment during get as well:
iova & (PAGE_SIZE-1) == umem->addr & (PAGE_SIZE-1)
But yes, this is the right idea
Jason
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