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ftrace: Avoid potential division by zero in function profiler

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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>
This commit is contained in:
Wen Yang 2020-01-03 11:02:48 +08:00 committed by Greg Kroah-Hartman
parent d89a351b08
commit 010a7e846d
1 changed files with 3 additions and 3 deletions
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6
kernel/trace/ftrace.c
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@ -554,8 +554,7 @@ static int function_stat_show(struct seq_file *m, void *v)
} }
#ifdef CONFIG_FUNCTION_GRAPH_TRACER #ifdef CONFIG_FUNCTION_GRAPH_TRACER
avg = rec->time; avg = div64_ul(rec->time, rec->counter);
do_div(avg, rec->counter);
if (tracing_thresh && (avg < tracing_thresh)) if (tracing_thresh && (avg < tracing_thresh))
goto out; goto out;
#endif #endif
@ -581,7 +580,8 @@ static int function_stat_show(struct seq_file *m, void *v)
* Divide only 1000 for ns^2 -> us^2 conversion. * Divide only 1000 for ns^2 -> us^2 conversion.
* trace_print_graph_duration will divide 1000 again. * 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); trace_seq_init(&s);