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()'
- 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().
I'm thinking the below patch on top should ammend these issues; please
verify.
---
--- 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);
