On Wed, Jan 05, 2022 at 11:50:33AM IST, Alexei Starovoitov wrote:

On Sun, Jan 02, 2022 at 09:51:15PM +0530, Kumar Kartikeya Dwivedi wrote:

quoted

This adds a complete test case to ensure we never take references to
modules not in MODULE_STATE_LIVE, which can lead to UAF, and it also
ensures we never access btf->kfunc_set_tab in an inconsistent state.

The test uses userfaultfd to artifically widen the race.

Fancy!
Does it have to use a different module?
Can it be part of bpf_testmod somehow?

I was thinking of doing it with bpf_testmod, but then I realised it would be a
problem with parallel mode of test_progs, where another selftest in parallel may
rely on bpf_testmod (which this test would unload, load and make it fault, and
then fail the load before restoring it by loading again), so I went with
bpf_testmod.

Maybe we can hardcode a list of tests to be executed serially in --workers=n > 1
mode? All serial tests are then executed in the beginning (or end), and then it
starts invoking others in parallel as usual.

--
Kartikeya