[PATCH 1/4] tracing/ftrace: Fixes unexpected -EINVAL when longest tracer name is set

[PATCH 1/4] tracing/ftrace: Fixes unexpected -EINVAL when longest tracer name is set

[Frederic Weisbecker]

Impact: Corrects return value from tracing_set_trace_write

The following commit d9e540762f5cdd89f24e518ad1fd31142d0b9726 remade
alive the bug which made the set of a new tracer returning -EINVAL if
this is the longest name of tracer.
This patch corrects it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 kernel/trace/trace.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4a90462..2d5672d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2655,6 +2655,9 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
 	char buf[max_tracer_type_len+1];
 	int i;
 	size_t ret;
+	int err;
+
+	ret = cnt;
 
 	if (cnt > max_tracer_type_len)
 		cnt = max_tracer_type_len;
@@ -2668,12 +2671,11 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
 	for (i = cnt - 1; i > 0 && isspace(buf[i]); i--)
 		buf[i] = 0;
 
-	ret = tracing_set_tracer(buf);
-	if (!ret)
-		ret = cnt;
+	err = tracing_set_tracer(buf);
+	if (err)
+		return err;
 
-	if (ret > 0)
-		filp->f_pos += ret;
+	filp->f_pos += ret;
 
 	return ret;
 }
-- 
1.5.2.5