| Message ID | 20221117214249.2addbe10@gandalf.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | tracing: Fix race where eprobes can be called before the event | expand |
On Thu, 17 Nov 2022 21:42:49 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > The flag that tells the event to call its triggers after reading the event > is set for eprobes after the eprobe is enabled. This leads to a race where > the eprobe may be triggered at the beginning of the event where the record > information is NULL. The eprobe then dereferences the NULL record causing > a NULL kernel pointer bug. > > Test for a NULL record to keep this from happening. > > Link: https://lore.kernel.org/linux-trace-kernel/20221116192552.1066630-1-rafaelmendsr@gmail.com/ This looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> BTW, would other trigger callbacks also need to add similar checks? Thank you, > > Cc: stable@vger.kernel.org > Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events") > Reported-by: Rafael Mendonca <rafaelmendsr@gmail.com> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/trace_eprobe.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c > index 5dd0617e5df6..6b31b74954d9 100644 > --- a/kernel/trace/trace_eprobe.c > +++ b/kernel/trace/trace_eprobe.c > @@ -563,6 +563,9 @@ static void eprobe_trigger_func(struct event_trigger_data *data, > { > struct eprobe_data *edata = data->private_data; > > + if (unlikely(!rec)) > + return; > + > __eprobe_trace_func(edata, rec); > } > > -- > 2.35.1 >
On Fri, 18 Nov 2022 21:18:09 +0900 Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > This looks good to me. > > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > BTW, would other trigger callbacks also need to add similar checks? I just checked, and yes, I think that histograms (the only other trigger that has EVENT_CMD_FL_NEEDS_REC set) has the same issue, and requires: diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 087c19548049..1c82478e8dff 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -5143,6 +5143,9 @@ static void event_hist_trigger(struct event_trigger_data *data, void *key = NULL; unsigned int i; + if (unlikely(!rbe)) + return; + memset(compound_key, 0, hist_data->key_size); for_each_hist_key_field(i, hist_data) { I'll add that next. -- Steve
diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index 5dd0617e5df6..6b31b74954d9 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -563,6 +563,9 @@ static void eprobe_trigger_func(struct event_trigger_data *data, { struct eprobe_data *edata = data->private_data; + if (unlikely(!rec)) + return; + __eprobe_trace_func(edata, rec); }