Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 3 Oct 2014 14:15:24 -0700 | Subject | Re: [PATCH] x86,seccomp,prctl: Remove PR_TSC_SIGSEGV and seccomp TSC filtering |
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On Fri, Oct 3, 2014 at 2:12 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Fri, Oct 03, 2014 at 02:04:53PM -0700, Andy Lutomirski wrote: >> On Fri, Oct 3, 2014 at 2:02 PM, Peter Zijlstra <peterz@infradead.org> wrote: > >> > Something like so.. slightly less ugly and possibly with more >> > complicated conditions setting the cr4 if you want to fix tsc vs seccomp >> > as well. >> >> This will crash anything that tries rdpmc in an allow-everything >> seccomp sandbox. It's also not very compatible with my grand scheme >> of allowing rdtsc to be turned off without breaking clock_gettime. :) > > Well, we clear cap_user_rdpmc, so everybody who still tries it gets what > he deserves, no problem there.
Oh, interesting.
To continue playing devil's advocate, what if you do perf_event_open, then mmap it, then start the seccomp sandbox?
My draft patches are currently tracking the number of perf_event mmaps per mm. I'm not thrilled with it, but it's straightforward. And I still need to benchmark cr4 writes, which is tedious, because I can't do it from user code.
--Andy
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