drm/i915: fix task reference leak in i915_debugfs.c

Leak a task reference in i915_ppgtt_info(), add put_task_struct()
to fix it.

Introduced by

commit 1c60fef535d143860d5bf6593e24ab6417f5227c
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Fri Dec 6 14:11:30 2013 -0800

    drm/i915: Dump all ppgtt

Signed-off-by: Geliang Tang <geliangtang@163.com>
[danvet: Add note provided by Jani about which commit introduced this
issue.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 5615d3d3ab59..879771766973 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2288,9 +2288,13 @@ static int i915_ppgtt_info(struct seq_file *m, void *data)
 
         list_for_each_entry_reverse(file, &dev->filelist, lhead) {
                 struct drm_i915_file_private *file_priv = file->driver_priv;
+                struct task_struct *task;
 
-                seq_printf(m, "\nproc: %s\n",
-                           get_pid_task(file->pid, PIDTYPE_PID)->comm);
+                task = get_pid_task(file->pid, PIDTYPE_PID);
+                if (!task)
+                        return -ESRCH;
+                seq_printf(m, "\nproc: %s\n", task->comm);
+                put_task_struct(task);
                 idr_for_each(&file_priv->context_idr, per_file_ctx,
                              (void *)(unsigned long)m);
         }