Messages in this thread | | | Date | Thu, 5 Sep 2019 23:13:47 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [patch 0/6] posix-cpu-timers: Fallout fixes and permission tightening |
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On Thu, 5 Sep 2019, Kees Cook wrote: > On Thu, Sep 05, 2019 at 02:03:39PM +0200, Thomas Gleixner wrote: > > Sysbot triggered an issue in the posix timer rework which was trivial to > > fix, but after running another test case I discovered that the rework broke > > the permission checks subtly. That's also a straightforward fix. > > > > Though when staring at it I discovered that the permission checks for > > process clocks and process timers are completely bonkers. The only > > requirement is that the target PID is a group leader. Which means that any > > process can read the clocks and attach timers to any other process without > > priviledge restrictions. > > > > That's just wrong because the clocks and timers can be used to observe > > behaviour and both reading the clocks and arming timers adds overhead and > > influences runtime performance of the target process. > > > > The last 4 patches deal with that and introduce ptrace based permission > > checks and also make the behaviour consistent between thread and process > > timers/clocks. > > I like these changes! Thanks for working on it. :) > > Since this is a subtle bit of checking and there are concerns about ABI > breaks, can you also write some selftests for this area just to nail > down what should work and what should be blocked, etc?
Sigh, yes. /me adds it to that append only todo list thingy :)
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