diff mbox series

[5.4,131/191] ftrace: Avoid potential division by zero in function profiler

Message ID 20200107205339.982782846@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg KH Jan. 7, 2020, 8:54 p.m. UTC 
From: Wen Yang <wenyang@linux.alibaba.com>

commit e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d upstream.

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.

Link: http://lkml.kernel.org/r/20200103030248.14516-1-wenyang@linux.alibaba.com

Cc: stable@vger.kernel.org
Fixes: e330b3bcd8319 ("tracing: Show sample std dev in function profiling")
Fixes: 34886c8bc590f ("tracing: add average time in function to function profiler")
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/trace/ftrace.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff mbox series

Patch

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -524,8 +524,7 @@  static int function_stat_show(struct seq
 	}
 
 #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
@@ -551,7 +550,8 @@  static int function_stat_show(struct seq
 		 * 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);