Re: [PATCH for-rc] RDMA: Fix ib block iterator counter overflow

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Jan 02, 2023 at 06:03:17PM +0200, Yonatan Nachum wrote:
> When registering a new DMA MR after selecting the best aligned page size
> for it, we iterate over the given sglist to split each entry to smaller,
> aligned to the selected page size, DMA blocks.
> 
> In given circumstances where the sg entry and page size fit certain sizes
> and the sg entry is not aligned to the selected page size, the total size
> of the aligned pages we need to cover the sg entry is >= 4GB.

Huh? The max length of a scatterlist element is unsigned int:

struct scatterlist {
	unsigned long	page_link;
	unsigned int	offset;
	unsigned int	length;

The problem is the construction of the end of iteration test:

	block_offset = biter->__dma_addr & (BIT_ULL(biter->__pg_bit) - 1);
	biter->__sg_advance += BIT_ULL(biter->__pg_bit) - block_offset;

	if (biter->__sg_advance >= sg_dma_len(biter->__sg)) {

This should be reworked so it doesn't increment until it knows it is
OK and leave the types alone.

Jason