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

commit 15544209cb0b5312e5220a9337a1fe61d1a1f2d9 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 9 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f064dfb973fe..8e8bb0e25489 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3950,8 +3950,7 @@ 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;
 
@@ -3997,9 +3996,9 @@ 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;
 
@@ -4022,8 +4021,7 @@ 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);
 
@@ -5563,7 +5561,7 @@ 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,
@@ -6149,7 +6147,7 @@ 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);