Messages in this thread Patch in this message | | | Date | Fri, 3 Sep 2021 00:02:46 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject_entry() |
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On Fri, 3 Sep 2021 03:30:34 +0000 Jiang Jiasheng <jiasheng@iscas.ac.cn> wrote:
> Directly use trace_event_buffer_reserve() might be unsafe,
How can it be unsafe?
> as we can see from the trace_trigger_soft_disabled() of > 'include/linux/trace_events.h' that if the value of > file->flags is 256, the check in the trace_trigger_soft_disabled() > will be passed but actually shouldn't have. > Therefore, we suggest that trace_trigger_soft_disabled() > should be added in front of the trace_event_buffer_reserve() > in trace_inject_entry().
Do you understand what the trace_inject_entry() does?
I'm not sure it makes sense to "soft disable" it.
> > Signed-off-by: Jiang Jiasheng <jiasheng@iscas.ac.cn> > --- > kernel/trace/trace_events_inject.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/trace/trace_events_inject.c b/kernel/trace/trace_events_inject.c > index c188045..6dfd3cd 100644 > --- a/kernel/trace/trace_events_inject.c > +++ b/kernel/trace/trace_events_inject.c > @@ -21,6 +21,8 @@ trace_inject_entry(struct trace_event_file *file, void *rec, int len) > void *entry; > > rcu_read_lock_sched(); > + if (trace_trigger_soft_disabled(file)) > + return written;
NACK!
The above introduces a major bug. Bonus points if you can figure out what that is yourself.
-- Steve
> entry = trace_event_buffer_reserve(&fbuffer, file, len); > if (entry) { > memcpy(entry, rec, len);
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