API and CLI are executed under the worker barrier by default in VPP, only the
VPP main thread runs, and workers are stopped.
For an API/CLI to be executed concurrently with workers, it must be explicitly
marked as such (mp_safe attribute).
It does not seem to be the case for ACL, so it should be fine.
Best
ben
> -----Original Message-----
> From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Chul-Woong
> Yang
> Sent: Monday, December 12, 2022 3:50
> To: vpp-dev@lists.fd.io
> Subject: [vpp-dev] Q) Is it a possible acl-plugin race condtion?
>
> Hi, team.
>
> I'm reading acl-plugin code and have a question on race condition.
> When vpp needs to update acl rules, it does not keep a refcnt or
> something and just `vec_free`s the rules. Is it safe?:
> ```
> /* ACL updater: from acl_add_list() */
> {
> a = am->acls + *acl_list_index;
> /* Get rid of the old rules */
> if (a->rules)
> vec_free (a->rules); /* (A) */
> }
> ...
>
>
> /* ACL user: from single_acl_match_5tuple() */
> for (i = 0; i < vec_len(acl_rules); i++)
> {
> r = &acl_rules[i];
> ... /* (B) */
> ```
>
> I worry that vpp can SEGV by refering freed memory when it referes an
> acl rules `r` in (B) while another thread frees the rule in (A).
>
> Best regards,
> Chul-Woong
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