tracing: Change tracing_buffers_fops to rely on tracing_get_cpu()

commit 46ef2be0d1d5ccea0c41bb606143586daadd537c upstream.

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

Change debugfs_create_file("trace_pipe_raw", data) caller to pass
"data = tr", tracing_buffers_open() can use tracing_get_cpu().

Change debugfs_create_file("snapshot_raw_fops", data) caller too,
this file uses tracing_buffers_open/release.

Link: http://lkml.kernel.org/r/20130723152600.GA23720@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8e8bb0e25489722bbf2d17be61436aa5d5248b42..7dcd67332f57925c74cb3cc55827ff357b647803 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4941,8 +4941,7 @@ static const struct file_operations snapshot_raw_fops = {
 
 static int tracing_buffers_open(struct inode *inode, struct file *filp)
 {
-       struct trace_cpu *tc = inode->i_private;
-       struct trace_array *tr = tc->tr;
+       struct trace_array *tr = inode->i_private;
        struct ftrace_buffer_info *info;
        int ret;
 
@@ -4961,7 +4960,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
        mutex_lock(&trace_types_lock);
 
        info->iter.tr           = tr;
-       info->iter.cpu_file     = tc->cpu;
+       info->iter.cpu_file     = tracing_get_cpu(inode);
        info->iter.trace        = tr->current_trace;
        info->iter.trace_buffer = &tr->trace_buffer;
        info->spare             = NULL;
@@ -5568,7 +5567,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
                                &data->trace_cpu, cpu, &tracing_fops);
 
        trace_create_cpu_file("trace_pipe_raw", 0444, d_cpu,
-                               &data->trace_cpu, cpu, &tracing_buffers_fops);
+                               tr, cpu, &tracing_buffers_fops);
 
        trace_create_cpu_file("stats", 0444, d_cpu,
                                &data->trace_cpu, cpu, &tracing_stats_fops);
@@ -5581,7 +5580,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
                                &data->trace_cpu, cpu, &snapshot_fops);
 
        trace_create_cpu_file("snapshot_raw", 0444, d_cpu,
-                               &data->trace_cpu, cpu, &snapshot_raw_fops);
+                               tr, cpu, &snapshot_raw_fops);
 #endif
 }