Multiple Linux Distributions Affected By Crippling Bug In Systemd (agwa.name)

An anonymous reader writes: System administrator Andrew Ayer has discovered a potentially critical bug in systemd which can bring a vulnerable Linux server to its knees with one command. "After running this command, PID 1 is hung in the pause system call. You can no longer start and stop daemons. inetd-style services no longer accept connections. You cannot cleanly reboot the system." According to the bug report, Debian, Ubuntu, and CentOS are among the distros susceptible to various levels of resource exhaustion. The bug, which has existed for more than two years, does not require root access to exploit.

Comments

I don't hate on systemd but this is really bad

[haruchai]

and been around for 2 years and doesn't require root access??
If this happened on Windows, I & many others would be scornful of it.

And of course the systemd devs throw a tantrum

[Anonymous Coward]

https://medium.com/@davidtstrauss/how-to-throw-a-tantrum-in-one-blog-post-c2ccaa58661d
Can't have anyone criticizing any aspect of the holy systemd.
Whole thing boils down to:
"Following security practices in an init system is hard, and you've never done it so leave us alone."
Completely ignoring the fact that the only reason they patched this thing is because he made a big deal out of it.
And on what planet is testing for corner cases like empty strings the domain of fuzz tools?
That seems like a pretty standard test case to me.
I can understand if you don't test for a 1MB string, but empty seems like a no brainer.

Re:RTFA, please.

[grcumb]

That is far from a detailed description and more of a list of uninformed rants. Much better to read the informed reply to TFA here: https://medium.com/@davidtstra...

More clueless autonomic defensiveness without any reflection on what the impact of the bug actually is. I especially enjoyed this old chestnut as the author attempts to fisk the original bug report:

These accusations are true for every major production kernel (Windows, Linux, and BSD) and every alternative to systemd (in the sense that they’re almost all written in C and run many of their operations as root).

"SystemD, let me just stop you there. I know the Linux kernel. I've worked with the Linux kernel. You're no Linux kernel."

The incredible hubris of asserting parity with the core of the entire OS, the ignorance that underlies the statement that init was written in C and runs as root, so it's every bit as vulnerable... How the fuck do you even make code run? Do you even teh logic?

The SystemD team is the Microsoft of a new generation. Doubling down on their mistakes; shouting louder when they don't get their way; using every available ratiocination and intellectual contortion to excuse themselves; resorting to any means to make their strategy win, instead of stopping to ask themselves for once, 'Are we following a winning strategy here?'

Thank g*d I quit writing software last year. Dealing with Microsoft's mind-crushing blindness was enough for one lifetime. Now I can just grump about it and walk away.

Re:OpenRC

[Shane_Optima]

As far as I can tell, the problem is mostly one of personality and ideology. Poettering is a rather unpleasant person who is purposefully choosing to do things in an unnecessarily hostile and control-destroying manner, and Red Hat, while obviously having done tremendous things to help Linux over the years, has been in the business of promoting user-hostile asshatery and lock-in philosophies in recent years, something which hasn't been remarked on nearly as much as it should've (possibly because RHAT earned themselves too many OSS brownie points 10+ years ago and are still making useful contributions today.)

None of that excuses the legions of people around who have said that there was no problem with SysV, or that declarative syntax was worthless (tell that to someone who is trying to build a distro), or treated process control or containerization as inherently unworthy things to be concerned with. I do not say that systemd does these things especially well; I merely say that as concerns, they are intrinsically worthy of consideration.

And if you say that no one needs better containerization options or that stateless systems is a worthless concept or that Debian's old init scripts were the pinnacle of perfection, you clearly do not know what you are talking about. Red Hat does have some fiat sway, but if SysV init were easy to stick with we wouldn't have seen all of the major distros adopt systemd in lockstep. It's not completely worthless. Some of the problems it solves are indeed real. I'm not saying it's worth half a million lines of C code to solve those problems, but the problems are fact there.

But if you actually deny that any problems exist, you're basically just an unthinking hater and no one is paying you any attention except a certain subset of systemd haters who didn't need any more convincing.

This actually isn't so dissimilar to Trump and concerns over immigration or terrorism, but that's an analogy for another day.

Not surprising

[MrKaos]

I've made several requests for systemd proponents to supply a use case that SysV initd could not support and haven't received a satisfactory reply to this purely technical question. I was interested in what systemd could offer over initd. I find systemd proponents are overly veherment in their criticisms of initd proponents.

I sense this comes from an inability to address the issues raised and, perhaps a mindset that anyone who has an appreciation for initd's elegant power will simply be bulldozed into irrelevance. I think systemd's criticism of the rc scripts that starts a linux based system is valid criticism however we have to keep in mind that they were devised by Red Hat. It is dealing with rc shell scripts that are the brunt of the justification for systemd.

In that sense the unitd solution is tidy but also reveals the justification to replace initd is not based on a full understanding of its capabilities, or even an understanding of was it is, a process manager. rc scripts are only meant to prepare the system for entries in /etc/inittab, yet everyone tries to get everything done in rc, which serializes the Linux boot process. A parallell boot is completely achievable by using initd properly. I know there is more to it, like events and messaging, I'm just citing one example.

Yet I've never seen a Linux distro that's utilized initd's /etc/inittab file properly. Especially a Red Hat system. They don't use initd properly, the rc scripts are bloated with rewrites of what initd already does, and now we're replacing initd, keh? initd has yet to be utilized fully on modern linux systems.

Criticisms of sco the company aside: sco *as a distribution of unix* had an interesting adjunct feature to initd, the 'enable' and 'disable' command that managed entries in /etc/inittab, where you would configure the characteristics of the system you were running. Franky I think this is functionality is essentially

sed -i -e '/someProcess/ s/:on:/:off:/' /etc.inittab ; kill -1 1

I think initd would make a lot more sense to more people if this functionality had been available in Linux from the beginning. It is true that initd is beguiling in terms of it's simplicity wrt its power, but it is also very worthwhile. It is supposed to be small as that is where the skill is expressed.

initd is where you design the characteristics of the system, it is not an event manager and all the other things systemd is supposed to be. Something that does all the functionality systemd has, belongs as an inittab enty, not as the first process the kernel runs.

The point of a bug like this is not that it is a big deal itself, the big deal is the failure mode systemd has been revealed to have due to its complexity. This the type of concern I have about systemd, what else can trigger such a failure mode. I have seen initd in a variety of failure modes and not once has it ever consumed all system resources and disconnected running processes.

Now we've seen systemd do something that initd can't.