tracing/function-graph: Use correct string size for snprintf

The nsecs_str string is a local variable defined as:

char nsecs_str[5];

It is possible for the snprintf call to use a size value larger than the
size of the string. This should not cause a buffer overrun as it is
written now due to the value for the string format "%03lu" can not be
larger than 1000. However, this change makes it correct. By making the
size correct we guard against potential future changes that could actually
cause a buffer overrun.

Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
LKML-Reference: <1276619355-18116-1-git-send-email-chase.douglas@canonical.com>

[ added 'UL' to number 8 to fix gcc warning comparing it to sizeof() ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 79f4bac..6bff236 100644 (file)
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -641,7 +641,8 @@ trace_print_graph_duration(unsigned long long duration, struct trace_seq *s)
 
        /* Print nsecs (we don't want to exceed 7 numbers) */
        if (len < 7) {
-               snprintf(nsecs_str, 8 - len, "%03lu", nsecs_rem);
+               snprintf(nsecs_str, min(sizeof(nsecs_str), 8UL - len), "%03lu",
+                        nsecs_rem);
                ret = trace_seq_printf(s, ".%s", nsecs_str);
                if (!ret)
                        return TRACE_TYPE_PARTIAL_LINE;