The 4.13 Linux kernel has been released

jeremy · 09-04-2017, 09:48 AM

From LWN:

Quote:

Linus has released the 4.13 kernel, right on schedule. Headline features in this release include kernel hardening via structure layout randomization, native TLS protocol support, better huge-page swapping, improved handling of writeback errors, better asynchronous I/O support, better power management via next-interrupt prediction, the elimination of the DocBook toolchain for formatted documentation, and more. There is one other change that is called out explicitly in the announcement: "The change in question is simply changing the default cifs behavior: instead of defaulting to SMB 1.0 (which you really should not use: just google for 'stop using SMB1' or similar), the default cifs mount now defaults to a rather more modern SMB 3.0."

The full release email:

Quote:

So last week was actually somewhat eventful, but not enough to push me
to delay 4.13.

Most of the changes since rc7 are actually networking fixes, the bulk
of them to various drivers. With apologies to the authors of said
patches, they don't look all that interesting (which is definitely
exactly what you want just before a release). Details in the appended
shortlog.

Note that the shortlog below is obviously only since rc7 - the _full_
4.13 log is much too big to post and nobody sane would read it. So if
you're interested in all the rest of it, get the git tree and limit
the logs to the files you are interested in if you crave details.

No, the excitement was largely in the mmu notification layer, where we
had a fairly last-minute regression and some discussion about the
problem. Lots of kudos to Jérôme Glisse for jumping on it, and
implementing the fix.

What's nice to see is that the regression pointed out a nasty and not
very well documented (or thought out) part of the mmu notifiers, and
the fix not only fixed the problem, but did so by cleaning up and
documenting what the right behavior should be, and furthermore did so
by getting rid of the problematic notifier and actually removing
almost two hundred lines in the process.

I love seeing those kinds of fixes. Better, smaller, code.

The other excitement this week was purely personal, consisting of
seven hours of pure agony due to a kidney stone. I'm all good, but it
sure _felt_ a lot longer than seven hours, and I don't even want to
imagine what it is for people that have had the experience drag out
for longer. Ugh.

Anyway, on to actual 4.13 issues.

While we've had lots of changes all over (4.13 was not particularly
big, but even a "solidly average" release is not exactly small), one
very _small_ change merits some extra attention, because it's one of
those very rare changes where we change behavior due to security
issues, and where people may need to be aware of that behavior change
when upgrading.

This time it's not really a kernel security issue, but a generic
protocol security issue.

The change in question is simply changing the default cifs behavior:
instead of defaulting to SMB 1.0 (which you really should not use:
just google for "stop using SMB1" or similar), the default cifs mount
now defaults to a rather more modern SMB 3.0.

Now, because you shouldn't have been using SMB1 anyway, this shouldn't
affect anybody. But guess what? It almost certainly does affect some
people, because they blithely continued using SMB1 without really
thinking about it.

And you certainly _can_ continue to use SMB1, but due to the default
change, now you need to be *aware* of it. You may need to add an
explicit "vers=1.0" to your mount options in /etc/fstab or similar if
you *really* want SMB1.

But if the new default of 3.0 doesn't work (because you still use a
pterodactyl as a windshield wiper), before you go all the way back to
the bad old days and use that "vers=1.0", you might want to try
"vers=2.1". Because let's face it, SMB1 is just bad, bad, bad.

Anyway, most people won't notice at all. And the ones that do notice
can check their current situation (just look at the output of "mount"
and see if you have any cifs things there), and you really should
update from the default even if you are *not* upgrading kernels.

Ok, enough about that. It was literally a two-liner change top
defaults - out of the million or so lines of the full 4.13 patch
changing real code.

Go get the new kernel,

Linus

Are any LQ members running 4.13 yet?

--jeremy

GazL · 09-04-2017, 10:18 AM

Built it this morning. The only issues I've encountered so far were ones that I was already experiencing with 4.12.y. Still early days though.

hifi100 · 11-19-2017, 07:57 PM

Code:

$ uname -a
Linux mypc 4.13.0-16-generic #19-Ubuntu SMP Wed Oct 11 18:35:14 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Code:

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu Bionic Beaver (development branch)
Release:	18.04
Codename:	bionic