From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 99DF4C6FA86 for ; Thu, 22 Sep 2022 09:37:10 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 00BAD10EA85; Thu, 22 Sep 2022 09:37:10 +0000 (UTC) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id CBA5B10EA8D for ; Thu, 22 Sep 2022 09:37:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663839426; x=1695375426; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=7gyvgtlWZWPdY2HAOZWMHNvyrcx9AjAPrLLRCh6JAxw=; b=gKTjNzRprDW/S+FwEhq4LfJaFgckVDkfp4qigAPI4kXWL6DNkvxRBmGM CCMhB/CemyQuTHoM/9oilvL72XZJLV/JuqckqFfL4DZ7LWHShvJttl3O5 X8V+TYM+YSQVS7t0H86cRU4083cU7Vlf8OSoLCkvEOEpBfx0lCXHHcbcV 6/wMhvDxcc8/YKq+5g+eyNhO7EcfqUENWH7Z/0v8A2cqttTh22oAkbnn/ yUd1Npfw4oHCBWQsUKiXfLi6sB4dJ6bP6vUxBfOv6naFO5RpsFzR1DobY EXvn5lwToYnIYmdqNWJ5dVepfFBIoML6hONBbKHIDOhwVz/Lm329s927G Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10477"; a="287331030" X-IronPort-AV: E=Sophos;i="5.93,335,1654585200"; d="scan'208";a="287331030" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2022 02:37:06 -0700 X-IronPort-AV: E=Sophos;i="5.93,335,1654585200"; d="scan'208";a="650451862" Received: from emurphy-mobl.ger.corp.intel.com (HELO [10.213.205.83]) ([10.213.205.83]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2022 02:37:04 -0700 Message-ID: <27158ebf-24e4-c519-13a5-f3d91a539ea2@linux.intel.com> Date: Thu, 22 Sep 2022 10:37:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Content-Language: en-US To: "Das, Nirmoy" , Nirmoy Das , intel-gfx@lists.freedesktop.org References: <20220908200706.25773-1-nirmoy.das@intel.com> <2cd5568f-e63c-1ae3-6aa9-809be360a397@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915: Fix a potential UAF at device unload X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: matthew.auld@intel.com, Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 21/09/2022 16:53, Das, Nirmoy wrote: > > On 9/9/2022 10:55 AM, Tvrtko Ursulin wrote: >> >> On 08/09/2022 21:07, Nirmoy Das wrote: >>> i915_gem_drain_freed_objects() might not be enough to >>> free all the objects and RCU delayed work might get >>> scheduled after the i915 device struct gets freed. >>> >>> Call i915_gem_drain_workqueue() to catch all RCU delayed work. >>> >>> Suggested-by: Chris Wilson >>> Signed-off-by: Nirmoy Das >>> --- >>>   drivers/gpu/drm/i915/i915_gem.c | 2 +- >>>   1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/i915/i915_gem.c >>> b/drivers/gpu/drm/i915/i915_gem.c >>> index 0f49ec9d494a..e8a053eaaa89 100644 >>> --- a/drivers/gpu/drm/i915/i915_gem.c >>> +++ b/drivers/gpu/drm/i915/i915_gem.c >>> @@ -1254,7 +1254,7 @@ void i915_gem_init_early(struct >>> drm_i915_private *dev_priv) >>>     void i915_gem_cleanup_early(struct drm_i915_private *dev_priv) >>>   { >>> -    i915_gem_drain_freed_objects(dev_priv); >>> +    i915_gem_drain_workqueue(dev_priv); >>>       GEM_BUG_ON(!llist_empty(&dev_priv->mm.free_list)); >>>       GEM_BUG_ON(atomic_read(&dev_priv->mm.free_count)); >>>       drm_WARN_ON(&dev_priv->drm, dev_priv->mm.shrink_count); >> >> >> Help me spot the place where RCU free worker schedules itself back to >> free more objects - if I got the rationale here right? > (Sorry for late reply, was on leave last week.) > > I had to clarify this with Chris. So when driver frees a obj, it does > dma_resv_fini() which will drop reference > > for all the fences in it and a fence might  reference to an object and > upon release of that fence can trigger a  release reference to an object. Hmm I couldn't find that in code but never mind. It's just a stronger version of the same flushing and it's not on a path where speed matters so feel free to go with it. Regards, Tvrtko