On Mon, Oct 14, 2019 at 11:35:44AM +0200, Peter Zijlstra wrote:
> On Fri, Oct 11, 2019 at 12:03:30PM -0400, Joel Fernandes (Google) wrote:
>
> > @@ -4761,6 +4762,7 @@ int perf_event_release_kernel(struct perf_event *event)
> > }
> >
> > no_ctx:
> > + security_perf_event_free(event);
> > put_event(event); /* Must be the 'last' reference */
> > return 0;
> > }
>
> > @@ -10553,11 +10568,16 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
> > }
> > }
> >
> > + err = security_perf_event_alloc(event);
> > + if (err)
> > + goto err_security;
> > +
> > /* symmetric to unaccount_event() in _free_event() */
> > account_event(event);
> >
> > return event;
> >
> > +err_security:
> > err_addr_filters:
> > kfree(event->addr_filter_ranges);
> >
>
> There's a bunch of problems here I think:
>
> - err_security is named wrong; the naming scheme is to name the label
> after the last thing that succeeded / first thing that needs to be
> undone.
>
> - per that, you're forgetting to undo 'get_callchain_buffers()'
Yes, you're right. Tested your fix below. Sorry to miss this.
> - perf_event_release_kernel() is not a full match to
> perf_event_alloc(), inherited events get created by
> perf_event_alloc() but never pass through
> perf_event_release_kernel().
Oh, through inherit_event(). Thanks for pointing this semantic out, did not
know that.
> I'm thinking the below patch on top should ammend these issues; please
> verify.
Yes, applied your diff below and verified that the events are getting freed
as they were in my initial set of tests. The diff also looks good to me.
I squashed your diff below and will resend as v3. Since you modified this
patch a lot, I will add your Co-developed-by tag as well.
thanks, Peter!
- Joel
> ---
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4540,6 +4540,8 @@ static void _free_event(struct perf_even
>
> unaccount_event(event);
>
> + security_perf_event_free(event);
> +
> if (event->rb) {
> /*
> * Can happen when we close an event with re-directed output.
> @@ -4774,7 +4776,6 @@ int perf_event_release_kernel(struct per
> }
>
> no_ctx:
> - security_perf_event_free(event);
> put_event(event); /* Must be the 'last' reference */
> return 0;
> }
> @@ -10595,14 +10596,18 @@ perf_event_alloc(struct perf_event_attr
>
> err = security_perf_event_alloc(event);
> if (err)
> - goto err_security;
> + goto err_callchain_buffer;
>
> /* symmetric to unaccount_event() in _free_event() */
> account_event(event);
>
> return event;
>
> -err_security:
> +err_callchain_buffer:
> + if (!event->parent) {
> + if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
> + put_callchain_buffers();
> + }
> err_addr_filters:
> kfree(event->addr_filter_ranges);
>
