[PATCH] drm/hisilicon: Fix a NULL pointer access when hibmc_load failed

[oushixiong1025 at 163.com]

From: Shixiong Ou <oushixiong at kylinos.cn>

[WHY]
If Calling hibmc_mm_init() failed in hibmc_load(), the hibmc_unload()
will access a NULL pointer, as it don't call ww_mutex_init() to
initialize mode_config.connection_mutex but try to lock it when
calling drm_atomic_helper_shutdown().

[   50.939211][  0] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018
	......
[   51.149882][  0] Call trace:
[   51.152750][  0]  ww_mutex_lock+0xf0/0x1e0
[   51.156829][  0]  drm_modeset_lock+0x184/0x2c0
[   51.161254][  0]  drm_modeset_lock_all_ctx+0x98/0x188
[   51.166284][  0]  drm_atomic_helper_shutdown+0xa4/0x128
[   51.171487][  0]  hibmc_unload+0x50/0x2f0
[   51.175479][  0]  hibmc_load+0x5d8/0x888
[   51.179386][  0]  drm_dev_register+0x280/0x558
[   51.183811][  0]  drm_get_pci_dev+0x140/0x3c8
[   51.188150][  0]  hibmc_pci_probe+0x148/0x190
[   51.192489][  0]  local_pci_probe+0xc4/0x180
[   51.196742][  0]  pci_device_probe+0x328/0x530
[   51.201167][  0]  really_probe+0x498/0x9a0
[   51.205248][  0]  driver_probe_device+0x224/0x308
[   51.209932][  0]  device_driver_attach+0xec/0x128
[   51.214616][  0]  __driver_attach+0x144/0x280
[   51.218955][  0]  bus_for_each_dev+0x120/0x1a0
[   51.223380][  0]  driver_attach+0x48/0x60
[   51.227372][  0]  bus_add_driver+0x328/0x578
[   51.231625][  0]  driver_register+0x148/0x398
[   51.235965][  0]  __pci_register_driver+0x15c/0x1c8
[   51.240823][  0]  hibmc_init+0x2c/0x34
[   51.244557][  0]  do_one_initcall+0xc8/0x4a8
[   51.248810][  0]  kernel_init_freeable+0x678/0x75c
[   51.253582][  0]  kernel_init+0x18/0x128
[   51.257489][  0]  ret_from_fork+0x10/0x18

[HOW]
Do not call drm_atomic_helper_shutdown() if drmm_mode_config_init() failed.

Signed-off-by: Shixiong Ou <oushixiong at kylinos.cn>
---
 drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
index 768b97f9e74a..8edc83db2afb 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
+++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
@@ -323,29 +323,29 @@ static int hibmc_load(struct drm_device *dev)
 
 	ret = hibmc_hw_init(priv);
 	if (ret)
-		goto err;
+		goto err_return;
 
 	ret = drmm_vram_helper_init(dev, pci_resource_start(pdev, 0),
 				    pci_resource_len(pdev, 0));
 	if (ret) {
 		drm_err(dev, "Error initializing VRAM MM; %d\n", ret);
-		goto err;
+		goto err_return;
 	}
 
 	ret = hibmc_kms_init(priv);
 	if (ret)
-		goto err;
+		goto err_return;
 
 	ret = drm_vblank_init(dev, dev->mode_config.num_crtc);
 	if (ret) {
 		drm_err(dev, "failed to initialize vblank: %d\n", ret);
-		goto err;
+		goto err_unload;
 	}
 
 	ret = hibmc_msi_init(dev);
 	if (ret) {
 		drm_err(dev, "hibmc msi init failed, ret:%d\n", ret);
-		goto err;
+		goto err_unload;
 	}
 
 	/* reset all the states of crtc/plane/encoder/connector */
@@ -353,8 +353,9 @@ static int hibmc_load(struct drm_device *dev)
 
 	return 0;
 
-err:
+err_unload:
 	hibmc_unload(dev);
+err_return:
 	drm_err(dev, "failed to initialize drm driver: %d\n", ret);
 	return ret;
 }
-- 
2.17.1