linux-kernel - [PATCH] drm/radeon: don't add files at control minor debugfs directory

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Date:   Sat,  3 Dec 2016 15:47:00 +0100
From:   Nicolai Stange <nicstange@...il.com>
To:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Cc:     David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...el.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Nicolai Stange <nicstange@...il.com>
Subject: [PATCH] drm/radeon: don't add files at control minor debugfs directory

Since commit 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"), a
struct drm_device's ->control member is always NULL.

In the case of CONFIG_DEBUG_FS=y, radeon_debugfs_add_files() accesses
->control->debugfs_root though. This results in the following Oops:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
  IP: radeon_debugfs_add_files+0x90/0x100 [radeon]
  PGD 0
  Oops: 0000 [#1] SMP
  [...]
  Call Trace:
   ? work_on_cpu+0xb0/0xb0
   radeon_fence_driver_init+0x120/0x150 [radeon]
   si_init+0x122/0xd50 [radeon]
   ? _raw_spin_unlock_irq+0x2c/0x40
   ? device_pm_check_callbacks+0xb3/0xc0
   radeon_device_init+0x958/0xda0 [radeon]
   radeon_driver_load_kms+0x9a/0x210 [radeon]
   drm_dev_register+0xa9/0xd0 [drm]
   drm_get_pci_dev+0x9c/0x1e0 [drm]
   radeon_pci_probe+0xb8/0xe0 [radeon]
  [...]

Fix this by omitting the drm_debugfs_create_files() call for the
control minor debugfs directory which is now non-existent anyway.

Fixes: 8a357d10043c ("drm: Nerf DRM_CONTROL nodes")
Signed-off-by: Nicolai Stange <nicstange@...il.com>
---
Tested on top of next-20161202.
That 8a357d10043c ("drm: Nerf DRM_CONTROL nodes")
is in next since 20161201.

 drivers/gpu/drm/radeon/radeon_device.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index 60a8920..8a1df2a 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -1949,9 +1949,6 @@ int radeon_debugfs_add_files(struct radeon_device *rdev,
 	rdev->debugfs_count = i;
 #if defined(CONFIG_DEBUG_FS)
 	drm_debugfs_create_files(files, nfiles,
-				 rdev->ddev->control->debugfs_root,
-				 rdev->ddev->control);
-	drm_debugfs_create_files(files, nfiles,
 				 rdev->ddev->primary->debugfs_root,
 				 rdev->ddev->primary);
 #endif
@@ -1966,9 +1963,6 @@ static void radeon_debugfs_remove_files(struct radeon_device *rdev)
 	for (i = 0; i < rdev->debugfs_count; i++) {
 		drm_debugfs_remove_files(rdev->debugfs[i].files,
 					 rdev->debugfs[i].num_files,
-					 rdev->ddev->control);
-		drm_debugfs_remove_files(rdev->debugfs[i].files,
-					 rdev->debugfs[i].num_files,
 					 rdev->ddev->primary);
 	}
 #endif
-- 
2.10.2