tracing: Reset iterator in t_start()

The iterator is m->private, but it's not reset to trace_types in
t_start(). If the output is larger than PAGE_SIZE and t_start()
is called the 2nd time, things will go wrong.

Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A418728.5020506@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 14 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 076fa6f0ee48..3bb31006b5cc 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2053,25 +2053,23 @@ static int tracing_open(struct inode *inode, struct file *file)
 static void *
 t_next(struct seq_file *m, void *v, loff_t *pos)
 {
-        struct tracer *t = m->private;
+        struct tracer *t = v;
 
         (*pos)++;
 
         if (t)
                 t = t->next;
 
-        m->private = t;
-
         return t;
 }
 
 static void *t_start(struct seq_file *m, loff_t *pos)
 {
-        struct tracer *t = m->private;
+        struct tracer *t;
         loff_t l = 0;
 
         mutex_lock(&trace_types_lock);
-        for (; t && l < *pos; t = t_next(m, t, &l))
+        for (t = trace_types; t && l < *pos; t = t_next(m, t, &l))
                 ;
 
         return t;
@@ -2107,18 +2105,10 @@ static struct seq_operations show_traces_seq_ops = {
 
 static int show_traces_open(struct inode *inode, struct file *file)
 {
-        int ret;
-
         if (tracing_disabled)
                 return -ENODEV;
 
-        ret = seq_open(file, &show_traces_seq_ops);
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                m->private = trace_types;
-        }
-
-        return ret;
+        return seq_open(file, &show_traces_seq_ops);
 }
 
 static ssize_t