On Thu, Aug 16, 2018 at 10:50:01AM +0800, Mao Wenan wrote: > There are five patches to fix CVE-2018-5390 in latest mainline > branch, but only two patches exist in stable 4.4 and 3.18: > dc6ae4d tcp: detect malicious patterns in tcp_collapse_ofo_queue() > 5fbec48 tcp: avoid collapses in tcp_prune_queue() if possible > I have tested with stable 4.4 kernel, and found the cpu usage was very high. > So I think only two patches can't fix the CVE-2018-5390. > test results: > with fix patch： 78.2% ksoftirqd > withoutfix patch： 90% ksoftirqd > > Then I try to imitate 72cd43ba(tcp: free batches of packets in tcp_prune_ofo_queue()) > to drop at least 12.5 % of sk_rcvbuf to avoid malicious attacks with simple queue > instead of RB tree. The result is not very well. > > After analysing the codes of stable 4.4, and debuging the > system, shows that search of ofo_queue(tcp ofo using a simple queue) cost more cycles. > > So I try to backport "tcp: use an RB tree for ooo receive queue" using RB tree > instead of simple queue, then backport Eric Dumazet 5 fixed patches in mainline, > good news is that ksoftirqd is turn to about 20%, which is the same with mainline now. > > Stable 4.4 have already back port two patches, > f4a3313d(tcp: avoid collapses in tcp_prune_queue() if possible) > 3d4bf93a(tcp: detect malicious patterns in tcp_collapse_ofo_queue()) > If we want to change simple queue to RB tree to finally resolve, we should apply previous > patch 9f5afeae(tcp: use an RB tree for ooo receive queue.) firstly, but 9f5afeae have many > conflicts with 3d4bf93a and f4a3313d, which are part of patch series from Eric in > mainline to fix CVE-2018-5390, so I need revert part of patches in stable 4.4 firstly, > then apply 9f5afeae, and reapply five patches from Eric. There seems to be an obvious mistake in one of the backports. Could you check the results with Takashi's follow-up fix submitted at http://lkml.kernel.org/r/20180815095846.7734-1-tiwai@xxxxxxx (I would try myself but you don't mention what test you ran.) Michal Kubecek
