[PATCH] trace-cmd: prevent print_graph_duration buffer overflow

[Chase Douglas <chase.douglas@canonical.com>]

Passing n > sizeof(string) to snprintf can cause a glibc buffer overflow
condition. We know the exact size of nsecs_str, so use it instead of
math that may overflow.

Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
---
 trace-ftrace.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/trace-ftrace.c b/trace-ftrace.c
index af9ac8d..ee7c6dc 100644
--- a/trace-ftrace.c
+++ b/trace-ftrace.c
@@ -148,7 +148,7 @@ static void print_graph_duration(struct trace_seq *s, unsigned long long duratio
 
 	/* Print nsecs (we don't want to exceed 7 numbers) */
 	if ((s->len - len) < 7) {
-		snprintf(nsecs_str, 8 - (s->len - len), "%03lu", nsecs_rem);
+		snprintf(nsecs_str, sizeof(nsecs_str), "%03lu", nsecs_rem);
 		trace_seq_printf(s, ".%s", nsecs_str);
 	}
 
-- 
1.7.0.4