Messages in this thread Patch in this message | | | From | Wen Yang <> | Subject | [PATCH] ftrace: avoid potential division by zero | Date | Wed, 1 Jan 2020 17:32:19 +0800 |
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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 --- kernel/trace/ftrace.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index ac99a35..a490ba5 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -527,7 +527,7 @@ 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(avg, rec->counter); if (tracing_thresh && (avg < tracing_thresh)) goto out; #endif @@ -553,7 +553,8 @@ 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
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