New Kernels: 5.2-rc6 and stable branch kernels 5.1.14 and 4.19.55 are now available with patch fixing Steam
5.1.14 and 4.19.55 were released just hours after 5.1.13 and 4.19.54. These kernels have a patch fixing the side-effect of the SACK vulnerability patches which broke Steam. 5.2-rc6 is a new release-candidate for the upcoming Linux 5.2 kernel. It is the release-candidate with the most updates of all 5.2 release candidates so far.
One does not simply Break User-space
Linus Torvalds has clearly stated that "WE DO NOT BREAK USERSPACE!" time and time again. This is more than a mere suggestion, it is a high priority. Naturally, Linus was all over it when Valve informed him that the patches for the SACK networking vulnerabilities has the side-effect of breaking the popular Steam gaming store. A patch was devised within hours and the Greg was promptly instructed to release updates to the stable kernel branches - which he did.
The patch fixing Steam is currently only available in 5.1.14, 4.19.55, 5.2-rc6 and git master. Greg Kroah-Hartman explained why on the LKML:
"This looks good for 4.19 and 5.1, so I'll push out new stable kernels in a bit for them.
But for 4.14 and older, we don't have the "hint" to know this is an outbound going packet and not to apply these checks at that point in time, so this patch doesn't work.
I'll see if I can figure anything else later this afternoon for those kernels..."
Updates for earlier supported stable branches (4.14, 4.9 and 4.4) will likely follow shortly.
Linux 5.2 rc6
This release-candidate had a unexpectedly large amounts of updates compared to the other release-candidates in the 5.2 series. Linus Torvalds had this to say about it:
I really was hoping that we'd continue to have an increasingly quiet and shrinking rc series. But that was not to be.
rc6 is the biggest rc in number of commits we've had so far for this 5.2 cycle (obviously ignoring the merge window itself and rc1). And it's not just because of trivial patches (although admittedly we have those too), but we obviously had the TCP SACK/fragmentation/mss fixes in there, and they in turn required some fixes too.
Happily we did pick up on the problem quickly - largely thanks to the patches making it into distro kernels quickly and then causing problems for the steam client of all things - but it's still something that doesn't exactly make me get the warm and fuzzies at this point in the release cycle.
I'm also doing this rc on a Saturday, because I am going to spend all of tomorrow on a plane once again. So I'm traveling first for a conference and then for some R&R on a liveaboard, so I'm going to have spotty access to email for a few days, and then for a week I'll be entirely incommunicado. So rc7 will be delayed.
I was thinking that I timed it all really well in what should be the quietest period of the release cycle for me, and now I obviously hope that last week really was a fluke.
Anyway, if something happens when I'm offline, Greg can presumably step up, although he'll have the same conference travel (but presumably at least the reverse jetlag ;)
With all that out of the way, I'm still reasonably optimistic that we're on track for a calm final part of the release, and I don't think there is anything particularly bad on the horizon.
And while we did have some excitement this week, _most_ of it by far was the usual small fixes. Including the by now expected SPDX updates, so the diffstat looks a bit messy again.
Anyway, ignoring the SPDX updates (and you should, even if they dominate the diffstat), about a quarter of the rc6 update is networking (the TCP fixes being a fairly small part of it - the bulk is still network driver and other networking fixes, including bpf). Another quarter is selftests (mostly bpf) and documentation.
The rest other driver updates (gpu, rdma, thunderbolt, usb..) arch updates (x86, risc-v and arm), and misc other updates (overlayfs etc).
But honestly, most of it really is pretty small (again - ignoring the SPDX noise), so despite my misgivings I don't think we're really in trouble.
Shortlog appended for the brave souls who want to look at details,
The new kernels are, as always, available at https://kernel.org/ and they will soon be in your favorite Linus distributions repositories.
published 2019-06-22 - last edited 2019-06-23