On Wed, Aug 09, 2017 at 12:01:53PM -0700, Kees Cook wrote:

This series is the result of Fabricio and I going around a few times
on possible solutions for finding a way to enhance RET_KILL to kill
the process group. There's a lot of ways this could be done, but I
wanted something that felt cleanest. As it happens, Tyler's recent
patch series for logging improvement also needs to know a litte bit
more during filter runs, and the solution for both is to pass back
the matched filter. This lets us examine it here for RET_KILL and
in the future for logging changes.

The filter passing is patch 1, the new flag for RET_KILL is patch 2.
Some test refactoring is in patch 3 for the RET_DATA ordering, and
patch 4 is the test for the new RET_KILL flag.

One thing missing is that CRIU will likely need to be updated, since
saving/restoring seccomp filter _rules_ will not include the filter
_flags_ for a process. This can be addressed separately.

Thanks for the heads up, I suppose PTRACE_SECCOMP_GET_FLAGS similar to
how PTRACE_SECCOMP_GET_FILTER works will be fine for this. One
question is: would we then also need to keep track of the TSYNC flag?
I don't think CRIU needs this to be correct, and we can grab the
KILL_PROCESS flag from filter->kill_process, so perhaps it's moot.

Anyway, happy to do this and the userspace part when this lands.

Cheers,

Tycho

Please take a look!

Thanks,

-Kees

v3:
- adjust seccomp_run_filters() to avoid later filters from masking
  kill-process RET_KILL actions (drewry)
- add test for masked RET_KILL.

v2:
- moved kill_process bool into struct padding gap (tyhicks)
- improved comments/docs in various places for clarify (tyhicks)
- use ASSERT_TRUE() for WIFEXITED and WIFSIGNALLED (tyhicks)
- adding Reviewed-bys from tyhicks

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