From patchwork Thu Feb 19 16:30:47 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Hoath X-Patchwork-Id: 5852521 Return-Path: X-Original-To: patchwork-intel-gfx@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 08DCABF440 for ; Thu, 19 Feb 2015 16:31:02 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3091C2028D for ; Thu, 19 Feb 2015 16:30:58 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id 4A5DA2027D for ; Thu, 19 Feb 2015 16:30:54 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6A4DD6E192; Thu, 19 Feb 2015 08:30:53 -0800 (PST) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by gabe.freedesktop.org (Postfix) with ESMTP id B0D3A6E5EB for ; Thu, 19 Feb 2015 08:30:52 -0800 (PST) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga103.fm.intel.com with ESMTP; 19 Feb 2015 08:23:14 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.09,609,1418112000"; d="scan'208";a="654419348" Received: from nthoath-linux.isw.intel.com ([10.102.226.65]) by orsmga001.jf.intel.com with ESMTP; 19 Feb 2015 08:30:50 -0800 From: Nick Hoath To: intel-gfx@lists.freedesktop.org Date: Thu, 19 Feb 2015 16:30:47 +0000 Message-Id: <1424363447-16296-1-git-send-email-nicholas.hoath@intel.com> X-Mailer: git-send-email 2.1.1 Subject: [Intel-gfx] [PATCH] drm/i915: Fix a use after free, and unbalanced refcounting X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88652 When converting from implicitly tracked execlist queue items to ref counted requests, not all frees of requests were replaced with unrefs, and extraneous refs/unrefs of contexts were added. Correct the unbalanced refcount & replace the frees. Remove a noisy warning when hitting the request creation path. drm_i915_gem_request and intel_context are both kref reference counted structures. Upon allocation, drm_i915_gem_request's ref count should be bumped using kref_init. When a context is assigned to the request, the context's reference count should be bumped using i915_gem_context_reference. i915_gem_request_reference will reduce the context reference count when the request is freed. Problem introduced in commit 6d3d8274bc45de4babb62d64562d92af984dd238 Author: Nick Hoath AuthorDate: Thu Jan 15 13:10:39 2015 +0000 drm/i915: Subsume intel_ctx_submit_request in to drm_i915_gem_request v2: Added comments explaining how the ctx pointer and the request object should be ref-counted. Removed noisy warning. v3: Cleaned up the language used in the commit & the header description (Thanks David Gordon) Signed-off-by: Nick Hoath Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he@intel.com) Reviewed-by: Thomas Daniel --- drivers/gpu/drm/i915/i915_drv.h | 11 ++++++++++- drivers/gpu/drm/i915/i915_gem.c | 3 +-- drivers/gpu/drm/i915/intel_lrc.c | 8 ++++---- 4 files changed, 16 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 2dedd43..956fe26 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2121,6 +2121,9 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old, * number comparisons on buffer last_read|write_seqno. It also allows an * emission time to be associated with the request for tracking how far ahead * of the GPU the submission is. + * + * The requests are reference counted, so upon creation they should have an + * initial reference taken using kref_init */ struct drm_i915_gem_request { struct kref ref; @@ -2144,7 +2147,16 @@ struct drm_i915_gem_request { /** Position in the ringbuffer of the end of the whole request */ u32 tail; - /** Context related to this request */ + /** + * Context related to this request + * Contexts are refcounted, so when this request is associated with a + * context, we must increment the context's refcount, to guarantee that + * it persists while any request is linked to it. Requests themselves + * are also refcounted, so the request will only be freed when the last + * reference to it is dismissed, and the code in + * i915_gem_request_free() will then decrement the refcount on the + * context. + */ struct intel_context *ctx; /** Batch buffer related to this request if any */ diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 61134ab..996f60f 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2664,8 +2664,7 @@ static void i915_gem_reset_ring_cleanup(struct drm_i915_private *dev_priv, if (submit_req->ctx != ring->default_context) intel_lr_context_unpin(ring, submit_req->ctx); - i915_gem_context_unreference(submit_req->ctx); - kfree(submit_req); + i915_gem_request_unreference(submit_req); } /* diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index aafcef3..62a2b2a 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -512,18 +512,19 @@ static int execlists_context_queue(struct intel_engine_cs *ring, * If there isn't a request associated with this submission, * create one as a temporary holder. */ - WARN(1, "execlist context submission without request"); request = kzalloc(sizeof(*request), GFP_KERNEL); if (request == NULL) return -ENOMEM; request->ring = ring; request->ctx = to; + kref_init(&request->ref); + request->uniq = dev_priv->request_uniq++; + i915_gem_context_reference(request->ctx); } else { + i915_gem_request_reference(request); WARN_ON(to != request->ctx); } request->tail = tail; - i915_gem_request_reference(request); - i915_gem_context_reference(request->ctx); intel_runtime_pm_get(dev_priv); @@ -740,7 +741,6 @@ void intel_execlists_retire_requests(struct intel_engine_cs *ring) if (ctx_obj && (ctx != ring->default_context)) intel_lr_context_unpin(ring, ctx); intel_runtime_pm_put(dev_priv); - i915_gem_context_unreference(ctx); list_del(&req->execlist_link); i915_gem_request_unreference(req); }