From: Wen Yang <wenyang@linux.alibaba.com>
To: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>
Cc: xlpang@linux.alibaba.com, Wen Yang <wenyang@linux.alibaba.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH v2] ftrace: avoid potential division by zero
Date: Fri, 3 Jan 2020 11:02:48 +0800 [thread overview]
Message-ID: <20200103030248.14516-1-wenyang@linux.alibaba.com> (raw)
The ftrace_profile->counter is unsigned long and
do_div truncates it to 32 bits, which means it can test
non-zero and be truncated to zero for division.
Fix this issue by using div64_ul() instead.
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-kernel@vger.kernel.org
---
v2: get rid of the pre-assigning of avg.
kernel/trace/ftrace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ac99a35..9bf1f2c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -526,8 +526,7 @@ static int function_stat_show(struct seq_file *m, void *v)
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- avg = rec->time;
- do_div(avg, rec->counter);
+ avg = div64_ul(rec->time, rec->counter);
if (tracing_thresh && (avg < tracing_thresh))
goto out;
#endif
@@ -553,7 +552,8 @@ static int function_stat_show(struct seq_file *m, void *v)
* Divide only 1000 for ns^2 -> us^2 conversion.
* trace_print_graph_duration will divide 1000 again.
*/
- do_div(stddev, rec->counter * (rec->counter - 1) * 1000);
+ stddev = div64_ul(stddev,
+ rec->counter * (rec->counter - 1) * 1000);
}
trace_seq_init(&s);
--
1.8.3.1
next reply other threads:[~2020-01-03 3:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-03 3:02 Wen Yang [this message]
2020-01-03 8:00 ` [PATCH v2] ftrace: avoid potential division by zero Justin Capella
2020-01-03 11:31 ` Wen Yang
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