diff options
| author | Wen Yang <wenyang@linux.alibaba.com> | 2020-01-03 11:02:48 +0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2020-04-28 19:03:14 +0100 |
| commit | c59e74104cfd7df3ca0b5f59f1baee9c8c28b9ef (patch) | |
| tree | 049cb030e291da57d8d223763bdf7883f935bca7 /kernel | |
| parent | 7fc973f532e791244b41eb9d0eb5dcc065e40b69 (diff) | |
| download | linux-stable-c59e74104cfd7df3ca0b5f59f1baee9c8c28b9ef.tar.gz linux-stable-c59e74104cfd7df3ca0b5f59f1baee9c8c28b9ef.tar.bz2 linux-stable-c59e74104cfd7df3ca0b5f59f1baee9c8c28b9ef.zip | |
ftrace: Avoid potential division by zero in function profiler
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
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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/ftrace.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index c59d43d54d32..ff5281a9c5d7 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -595,8 +595,7 @@ static int function_stat_show(struct seq_file *m, void *v) #ifdef CONFIG_FUNCTION_GRAPH_TRACER seq_printf(m, " "); - avg = rec->time; - do_div(avg, rec->counter); + avg = div64_ul(rec->time, rec->counter); /* Sample standard deviation (s^2) */ if (rec->counter <= 1) @@ -613,7 +612,8 @@ 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); |