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 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel