RE: [PATCH] drm/ttm: add a BUG_ON in ttm_set_driver_manager when array bounds

["Chen, Guchun" <Guchun.Chen@xxxxxxx>]

[Public]

 

Hi Christian and Xinhui,

 

Thanks for your suggestion. The cause is I saw data corruption in several proprietary use cases. BUILD_BUG_ON will have build variation per gcc difference?

 

Anyway, WARN_ON is fine to me, and I will send a new patch set soon to address this.

 

Regards,

Guchun

 

From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Friday, September 10, 2021 2:37 PM
To: Pan, Xinhui <Xinhui.Pan@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Chen, Guchun <Guchun.Chen@xxxxxxx>
Cc: Shi, Leslie <Yuliang.Shi@xxxxxxx>
Subject: Re: [PATCH] drm/ttm: add a BUG_ON in ttm_set_driver_manager when array bounds

 

Yeah, that's a good point.

If build_bug_on() doesn't works for some reason then we at least need to lower this to a WARN_ON.

A BUG_ON() is only justified if we prevent strong data corruption with it or note a NULL pointer earlier on or similar.

Regards,
Christian.

Am 10.09.21 um 06:36 schrieb Pan, Xinhui:

[AMD Official Use Only]

 

looks good to me.

But maybe build_bug_on works too and more reasonable to detect such wrong usage.

---

From: Chen, Guchun <Guchun.Chen@xxxxxxx>
Sent: Friday, September 10, 2021 12:30:14 PM
To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>; Pan, Xinhui <Xinhui.Pan@xxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>
Cc: Chen, Guchun <Guchun.Chen@xxxxxxx>; Shi, Leslie <Yuliang.Shi@xxxxxxx>
Subject: [PATCH] drm/ttm: add a BUG_ON in ttm_set_driver_manager when array bounds

 

Vendor will define their own memory types on top of TTM_PL_PRIV,
but call ttm_set_driver_manager directly without checking mem_type
value when setting up memory manager. So add such check to aware
the case when array bounds.

Signed-off-by: Leslie Shi <Yuliang.Shi@xxxxxxx>
Signed-off-by: Guchun Chen <guchun.chen@xxxxxxx>
---
 include/drm/ttm/ttm_device.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
index 7a0f561c57ee..24ad76ca8022 100644
--- a/include/drm/ttm/ttm_device.h
+++ b/include/drm/ttm/ttm_device.h
@@ -308,6 +308,7 @@ ttm_manager_type(struct ttm_device *bdev, int mem_type)
 static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
                                           struct ttm_resource_manager *manager)
 {
+       BUG_ON(type >= TTM_NUM_MEM_TYPES);
         bdev->man_drv[type] = manager;
 }
 
--
2.17.1