tracing: Change tracing_stats_fops to rely on tracing_get_cpu()

tracing_open_generic_tc() is racy, the memory inode->i_private
points to can be already freed.

1. Change one of its users, tracing_stats_fops, to use
   tracing_*_generic_tr() instead.

2. Change trace_create_cpu_file("stats", data) to pass "data = tr".

3. Change tracing_stats_read() to use tracing_get_cpu().

Link: http://lkml.kernel.org/r/20130723152603.GA23727@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 30c058a56ffb138deefd315e44e7f1fb5b9b9b23..e29dc8f69aac3a886f538b180cc94ccd598fea9b 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2982,7 +2982,6 @@ static int tracing_open_generic_tr(struct inode *inode, struct file *filp)
        filp->private_data = inode->i_private;
 
        return 0;
-       
 }
 
 static int tracing_open_generic_tc(struct inode *inode, struct file *filp)
@@ -5285,14 +5284,14 @@ static ssize_t
 tracing_stats_read(struct file *filp, char __user *ubuf,
                   size_t count, loff_t *ppos)
 {
-       struct trace_cpu *tc = filp->private_data;
-       struct trace_array *tr = tc->tr;
+       struct inode *inode = file_inode(filp);
+       struct trace_array *tr = inode->i_private;
        struct trace_buffer *trace_buf = &tr->trace_buffer;
+       int cpu = tracing_get_cpu(inode);
        struct trace_seq *s;
        unsigned long cnt;
        unsigned long long t;
        unsigned long usec_rem;
-       int cpu = tc->cpu;
 
        s = kmalloc(sizeof(*s), GFP_KERNEL);
        if (!s)
@@ -5345,10 +5344,10 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
 }
 
 static const struct file_operations tracing_stats_fops = {
-       .open           = tracing_open_generic_tc,
+       .open           = tracing_open_generic_tr,
        .read           = tracing_stats_read,
        .llseek         = generic_file_llseek,
-       .release        = tracing_release_generic_tc,
+       .release        = tracing_release_generic_tr,
 };
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -5578,7 +5577,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
                                tr, cpu, &tracing_buffers_fops);
 
        trace_create_cpu_file("stats", 0444, d_cpu,
-                               &data->trace_cpu, cpu, &tracing_stats_fops);
+                               tr, cpu, &tracing_stats_fops);
 
        trace_create_cpu_file("buffer_size_kb", 0444, d_cpu,
                                &data->trace_cpu, cpu, &tracing_entries_fops);