[PATCH 2/2] tracing/filters: fix off-by-one bug

[Li Zefan <lizf@cn.fujitsu.com>]

We should leave the last slot for the ending '\0'.

[ Impact: fix possible crash when the length of an operand is 128 ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/trace/trace_events_filter.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 22c2998..a7430b1 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -736,7 +736,7 @@ static inline void clear_operand_string(struct filter_parse_state *ps)
 
 static inline int append_operand_char(struct filter_parse_state *ps, char c)
 {
-	if (ps->operand.tail == MAX_FILTER_STR_VAL)
+	if (ps->operand.tail == MAX_FILTER_STR_VAL - 1)
 		return -EINVAL;
 
 	ps->operand.string[ps->operand.tail++] = c;
-- 
1.5.4.rc3