On Tue, Feb 25, 2020 at 02:04:51PM +1030, Alex Murray wrote: > > On Fri, Feb 21, 2020 at 02:04:37PM -0800, Kees Cook wrote: > >> On Thu, Feb 20, 2020 at 03:45:39AM +0000, Seth Arnold wrote: > >> > I'm worried that turning this flag on for the first time in an LTS > >> > release > >> > may be breaking too many expectations.
> >> > Adapting applications may be too much effort; because I don't know what > >> > exactly apport is doing here it is hard to estimate how much effort it > >> > will take to adapt it. Possibly the user-launched apport instances need > >> > to create their own directory on launch. Possibly apport needs a > >> > more invasive redesign. > >> > [...] > >> > Source code searching is not practical. The combination of working > >> > with files in a world-writable sticky directory and not already using > >> > O_EXCL with O_CREAT is not feasible to search for. > >> FWIW, I think that the scope of the change is small enough (only in > >> world-writable stick directories) and dramatic enough (usually total > >> failure), that the risk is worth the benefit. Excepting the very few > >> special directories (like /var/crash, where the software using them > >> is likely enumerable), I would also argue that breaking stuff in > >> "standard" temp directories (like /tmp) that isn't using O_EXCL is > >> actually _desirable_, given that it is expressly risky to operate in > >> that condition. > >> And, I would suggest that doing this in an LTS is the right thing to do, > >> otherwise you wait 2 years before gaining this defense that would be > >> actively _disabled_ compared to all other distros with a modern version > >> of systemd. And if this is the first noticed problem, that seems to be a > >> reasonably good indication of how rare the case is of it creating "real" > >> problems. > > As an additional wrinkle, procps in focal-proposed is now setting > > fs.protected_regular=2 by default, overriding the systemd setting. This > > hasn't made it out of proposed yet because the additional restriction broke > > the postgresql-common autopkgtest (fix for this is in progress): > > https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1864423 > > Kees, it sounds like you were advocating for setting the level to > > fs.protected_regular=1, but NOT raising it to 2. Should we back out this > > procps change for 20.04? > (I'll let Kees respond for himself but figured this was a good point to > reply) > From the Ubuntu Security team's view, it is not clear how much breakage > will result from setting this to 2 - setting protected_regular=1 is > already a good win and so far has seen little fallout that I know of > (Apport has already worked around this), but given how close we are to > FF I am a bit hesitant to mandate for this to be =2 (given we > already have one known failure as a result). From a security point of > view, =2 is a better default but this is not the only view that > matters. > So my preference would be to keep this at =2 for now but be confident > that we can back it out to =1 in the event that we suddenly discover a > bunch more issues in the near term. Thanks, it's easy enough to back out later (as long as someone actually raises a flag when things break!), so I'm ok with that. Since postgresql-common's tests have now been fixed for compatibility with =2, the procps with this new behavior will be unblocked and should reach the focal release today or tomorrow. -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer https://www.debian.org/ slanga...@ubuntu.com vor...@debian.org
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