tracing: Change tracing_pipe_fops() to rely on tracing_get_cpu()

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

Change debugfs_create_file("trace_pipe", data) callers to to pass
"data = tr", tracing_open_pipe() can use tracing_get_cpu().

Link: http://lkml.kernel.org/r/20130723152557.GA23717@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 cfff63c2148af0a65294f5593f970bd1e0c6eeb8..51a99ef2a6e5c23e49facf196f326e5a3238864d 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3959,8 +3959,7 @@ tracing_max_lat_write(struct file *filp, const char __user *ubuf,
 
 static int tracing_open_pipe(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 trace_iterator *iter;
        int ret = 0;
 
@@ -4006,9 +4005,9 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
        if (trace_clocks[tr->clock_id].in_ns)
                iter->iter_flags |= TRACE_FILE_TIME_IN_NS;
 
-       iter->cpu_file = tc->cpu;
-       iter->tr = tc->tr;
-       iter->trace_buffer = &tc->tr->trace_buffer;
+       iter->tr = tr;
+       iter->trace_buffer = &tr->trace_buffer;
+       iter->cpu_file = tracing_get_cpu(inode);
        mutex_init(&iter->mutex);
        filp->private_data = iter;
 
@@ -4031,8 +4030,7 @@ fail:
 static int tracing_release_pipe(struct inode *inode, struct file *file)
 {
        struct trace_iterator *iter = file->private_data;
-       struct trace_cpu *tc = inode->i_private;
-       struct trace_array *tr = tc->tr;
+       struct trace_array *tr = inode->i_private;
 
        mutex_lock(&trace_types_lock);
 
@@ -5571,7 +5569,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
 
        /* per cpu trace_pipe */
        trace_create_cpu_file("trace_pipe", 0444, d_cpu,
-                               &data->trace_cpu, cpu, &tracing_pipe_fops);
+                               tr, cpu, &tracing_pipe_fops);
 
        /* per cpu trace */
        trace_create_cpu_file("trace", 0644, d_cpu,
@@ -6157,7 +6155,7 @@ init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer)
                        (void *)&tr->trace_cpu, &tracing_fops);
 
        trace_create_file("trace_pipe", 0444, d_tracer,
-                       (void *)&tr->trace_cpu, &tracing_pipe_fops);
+                         tr, &tracing_pipe_fops);
 
        trace_create_file("buffer_size_kb", 0644, d_tracer,
                        (void *)&tr->trace_cpu, &tracing_entries_fops);