drm/i915: Avoid NULL ctx->obj dereference in debugfs/i915_context_info

In commit 691e6415c891b8b2b082a120b896b443531c4d45
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Wed Apr 9 09:07:36 2014 +0100

    drm/i915: Always use kref tracking for all contexts.

we populated fake contexts on all platforms. These were identical to the
full hardware context tracking structs, except for the ctx->obj used to
store the hardware state. However, there remained one place where we
assumed that if a context existed, it would have an object associated
with it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77717
Testcase: igt/drv_suspend/debugfs-reader
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index cad175c..18b3565 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1698,6 +1698,9 @@ static int i915_context_status(struct seq_file *m, void *unused)
        }
 
        list_for_each_entry(ctx, &dev_priv->context_list, link) {
+               if (ctx->obj == NULL)
+                       continue;
+
                seq_puts(m, "HW context ");
                describe_ctx(m, ctx);
                for_each_ring(ring, dev_priv, i)