* [PATCH] tracing: Fix race where eprobes can be called before the event
@ 2022-11-18 2:42 Steven Rostedt
2022-11-18 12:18 ` Masami Hiramatsu
0 siblings, 1 reply; 3+ messages in thread
From: Steven Rostedt @ 2022-11-18 2:42 UTC (permalink / raw)
To: LKML, Linux Trace Kernel
Cc: Masami Hiramatsu, Rafael Mendonca, Tzvetomir Stoyanov, Tom Zanussi
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/
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] tracing: Fix race where eprobes can be called before the event
2022-11-18 2:42 [PATCH] tracing: Fix race where eprobes can be called before the event Steven Rostedt
@ 2022-11-18 12:18 ` Masami Hiramatsu
2022-11-23 21:02 ` Steven Rostedt
0 siblings, 1 reply; 3+ messages in thread
From: Masami Hiramatsu @ 2022-11-18 12:18 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Linux Trace Kernel, Masami Hiramatsu, Rafael Mendonca,
Tzvetomir Stoyanov, Tom Zanussi
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
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tracing: Fix race where eprobes can be called before the event
2022-11-18 12:18 ` Masami Hiramatsu
@ 2022-11-23 21:02 ` Steven Rostedt
0 siblings, 0 replies; 3+ messages in thread
From: Steven Rostedt @ 2022-11-23 21:02 UTC (permalink / raw)
To: Masami Hiramatsu (Google)
Cc: LKML, Linux Trace Kernel, Rafael Mendonca, Tzvetomir Stoyanov,
Tom Zanussi
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2022-11-18 2:42 [PATCH] tracing: Fix race where eprobes can be called before the event Steven Rostedt
2022-11-18 12:18 ` Masami Hiramatsu
2022-11-23 21:02 ` Steven Rostedt
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