Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756910AbdDFMzN (ORCPT ); Thu, 6 Apr 2017 08:55:13 -0400 Received: from regular1.263xmail.com ([211.150.99.134]:34782 "EHLO regular1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932347AbdDFMzE (ORCPT ); Thu, 6 Apr 2017 08:55:04 -0400 X-263anti-spam: KSV:0; X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-KSVirus-check: 0 X-ABS-CHECKED: 4 X-RL-SENDER: jeffy.chen@rock-chips.com X-FST-TO: seanpaul@chromium.org X-SENDER-IP: 103.29.142.67 X-LOGIN-NAME: jeffy.chen@rock-chips.com X-UNIQUE-TAG: X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Message-ID: <58E63A88.4090108@rock-chips.com> Date: Thu, 06 Apr 2017 20:54:32 +0800 From: jeffy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20130126 Thunderbird/19.0 MIME-Version: 1.0 To: Sean Paul CC: linux-kernel@vger.kernel.org, briannorris@chromium.org, dianders@chromium.org, tfiga@chromium.org, zyw@rock-chips.com, mark.yao@rock-chips.com, Heiko Stuebner , dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, David Airlie , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3 8/9] drm/rockchip: gem: Don't alloc/free gem buf when dev_private is invalid References: <1491380967-28570-1-git-send-email-jeffy.chen@rock-chips.com> <1491380967-28570-9-git-send-email-jeffy.chen@rock-chips.com> <20170405162839.k6q4b3tpt6t2s3zm@art_vandelay> <58E5AC5F.5090303@rock-chips.com> <20170406122633.2t5hf25ozqoohnl2@art_vandelay> In-Reply-To: <20170406122633.2t5hf25ozqoohnl2@art_vandelay> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3272 Lines: 96 Hi Sean, On 04/06/2017 08:26 PM, Sean Paul wrote: > On Thu, Apr 06, 2017 at 10:47:59AM +0800, jeffy wrote: >> Hi Sean, >> >> On 04/06/2017 12:28 AM, Sean Paul wrote: >>> On Wed, Apr 05, 2017 at 04:29:26PM +0800, Jeffy Chen wrote: >>>> After unbinding drm, the userspace may still has a chance to access >>>> gem buf. >>>> >>>> Add a sanity check for a NULL dev_private to prevent that from >>>> happening. >>> >>> I still don't understand how this is happening. You're saying that these hooks >>> can be called after rockchip_drm_unbind() has finished? >>> >> yes, tested on chromebook rk3399 kevin with kernel 4.4, if trigger unbind >> without killing display service(ui or frecon): >> >> [ 31.276889] [] dump_backtrace+0x0/0x164 >> [ 31.282288] [] show_stack+0x24/0x30 >> [ 31.287338] [] dump_stack+0x98/0xb8 >> [ 31.292389] [] rockchip_gem_create_object+0x6c/0x2ec >> [ 31.298910] [] >> rockchip_gem_create_with_handle+0x38/0x10c >> [ 31.305868] [] rockchip_gem_create_ioctl+0x38/0x50 >> [ 31.312221] [] drm_ioctl+0x2bc/0x438 >> [ 31.317359] [] drm_compat_ioctl+0x3c/0x70 >> [ 31.322935] [] compat_SyS_ioctl+0x134/0x1048 >> [ 31.328766] [] __sys_trace_return+0x0/0x4 > > Hi Jeffy, > I'm not suggesting this doesn't happen, I believe you :-). I'd really like to > know *why* it happens. > > Are you sure that unbind has completely finished before this trace occurs? > Perhaps this is results from a race between unbind and gem allocate? yes, that unbind is finished. and it looks like the display server still holds drm dev fd(even it been deleted after unbind). sometimes i can see it trigger ioctl even seconds later. i'll send a patch to break drm_ioctl after unbind. > > Sean > >> >>> Sean >>> >>>> >>>> Signed-off-by: Jeffy Chen >>>> --- >>>> >>>> Changes in v3: >>>> Address Daniel Vetter 's comments. >>>> Update commit message. >>>> >>>> Changes in v2: None >>>> >>>> drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 8 ++++++++ >>>> 1 file changed, 8 insertions(+) >>>> >>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c >>>> index df9e570..205a3dc 100644 >>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c >>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c >>>> @@ -184,6 +184,9 @@ static int rockchip_gem_alloc_buf(struct rockchip_gem_object *rk_obj, >>>> struct drm_device *drm = obj->dev; >>>> struct rockchip_drm_private *private = drm->dev_private; >>>> >>>> + if (!private) >>>> + return -ENODEV; >>>> + >>>> if (private->domain) >>>> return rockchip_gem_alloc_iommu(rk_obj, alloc_kmap); >>>> else >>>> @@ -208,6 +211,11 @@ static void rockchip_gem_free_dma(struct rockchip_gem_object *rk_obj) >>>> >>>> static void rockchip_gem_free_buf(struct rockchip_gem_object *rk_obj) >>>> { >>>> + struct drm_device *drm = rk_obj->base.dev; >>>> + >>>> + if (!drm->dev_private) >>>> + return; >>>> + >>>> if (rk_obj->pages) >>>> rockchip_gem_free_iommu(rk_obj); >>>> else >>>> -- >>>> 2.1.4 >>>> >>> >> >