Re: [for-linus][PATCH 2/5] tracing/uprobe: Fix double perf_event linking on multiprobe uprobe

On Tue, Jan 21, 2020 at 09:38:49AM -0500, Steven Rostedt wrote:

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 4ee703728aec..03e4e180058d 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -230,6 +230,7 @@ struct trace_probe_event { struct trace_event_call call; struct list_head files; struct list_head probes;

• char data[0];

};

Note that this relies on pure 'luck'. If you stick anything <4 bytes in between the list_head and the data member it'll come unstuck real fast.

+static struct trace_uprobe_filter * +trace_uprobe_get_filter(struct trace_uprobe *tu) +{

• struct trace_probe_event *event = tu->tp.event;
• return (struct trace_uprobe_filter *)&event->data[0];

+}

That is, the above does not consider the alignment requirements of struct trace_uprobe_filter.