* [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject_entry()
@ 2021-09-03 3:30 Jiang Jiasheng
2021-09-03 4:02 ` Steven Rostedt
0 siblings, 1 reply; 2+ messages in thread
From: Jiang Jiasheng @ 2021-09-03 3:30 UTC (permalink / raw)
To: rostedt, mingo; +Cc: linux-kernel, Jiang Jiasheng
Directly use trace_event_buffer_reserve() might 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().
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;
entry = trace_event_buffer_reserve(&fbuffer, file, len);
if (entry) {
memcpy(entry, rec, len);
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject_entry()
2021-09-03 3:30 [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject_entry() Jiang Jiasheng
@ 2021-09-03 4:02 ` Steven Rostedt
0 siblings, 0 replies; 2+ messages in thread
From: Steven Rostedt @ 2021-09-03 4:02 UTC (permalink / raw)
To: Jiang Jiasheng; +Cc: mingo, linux-kernel
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);
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-09-03 3:30 [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject_entry() Jiang Jiasheng
2021-09-03 4:02 ` Steven Rostedt
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