Sorry to ping this but it's been a while. Robin, did you get a chance to resend your version?
Thanks Nicolin On Tue, Jul 02, 2019 at 02:04:01PM -0700, Nicolin Chen wrote: > On Tue, Jul 02, 2019 at 11:40:02AM +0100, Robin Murphy wrote: > > On reflection, I don't really think that size_t fits here anyway, since > > all the members of the incoming struct scatterlist are unsigned int too. > > Does the patch below work? > > Yes. > > > ----->8----- > > From: Robin Murphy <robin.mur...@arm.com> > > Subject: [PATCH] iommu/dma: Handle SG length overflow better > > > > Since scatterlist dimensions are all unsigned ints, in the relatively > > rare cases where a device's max_segment_size is set to UINT_MAX, then > > the "cur_len + s_length <= max_len" check in __finalise_sg() will always > > return true. As a result, the corner case of such a device mapping an > > excessively large scatterlist which is mergeable to or beyond a total > > length of 4GB can lead to overflow and a bogus truncated dma_length in > > the resulting segment. > > > > As we already assume that any single segment must be no longer than > > max_len to begin with, this can easily be addressed by reshuffling the > > comparison. > > > > Fixes: 809eac54cdd6 ("iommu/dma: Implement scatterlist segment merging") > > Reported-by: Nicolin Chen <nicoleots...@gmail.com> > > Signed-off-by: Robin Murphy <robin.mur...@arm.com> > > Tested-by: Nicolin Chen <nicoleots...@gmail.com> > > Thank you! > > > --- > > drivers/iommu/dma-iommu.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > > index 129c4badf9ae..8de6cf623362 100644 > > --- a/drivers/iommu/dma-iommu.c > > +++ b/drivers/iommu/dma-iommu.c > > @@ -721,7 +721,7 @@ static int __finalise_sg(struct device *dev, struct > > scatterlist *sg, int nents, > > * - and wouldn't make the resulting output segment too long > > */ > > if (cur_len && !s_iova_off && (dma_addr & seg_mask) && > > - (cur_len + s_length <= max_len)) { > > + (max_len - cur_len >= s_length)) { > > /* ...then concatenate it with the previous one */ > > cur_len += s_length; > > } else {