ring-buffer: check for divide by zero in ring-buffer-benchmark
Although we check if "missed" is not zero, we divide by hit + missed,
and the addition can possible overflow and become a divide by zero.
This patch checks for this case, and will report it when it happens
then modify "hit" to make the calculation be non zero.
[ Impact: prevent possible divide by zero in ring-buffer-benchmark ]
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 7d3aef9..8d68e14 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -294,6 +294,12 @@
pr_info("Total iterations per millisec: %ld\n", hit + missed);
+ /* it is possible that hit + missed will overflow and be zero */
+ if (!(hit + missed)) {
+ pr_info("hit + missed overflowed and totalled zero!\n");
+ hit--; /* make it non zero */
+ }
+
/* Caculate the average time in nanosecs */
avg = NSEC_PER_MSEC / (hit + missed);
pr_info("%ld ns per entry\n", avg);