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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A68CEC433DF for ; Thu, 28 May 2020 19:42:49 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 889472078C for ; Thu, 28 May 2020 19:42:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 889472078C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1457A6E0B7; Thu, 28 May 2020 19:42:49 +0000 (UTC) Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTPS id A922E6E0B7 for ; Thu, 28 May 2020 19:42:47 +0000 (UTC) IronPort-SDR: RW75Jr6tTuqJsOt6JHMvSS61FqE3HluEJI78mgob/L4uveS1TU+OohTlZhGzEKgAuCrgnbkvaM wCbTj5Ie6tzw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 May 2020 12:42:47 -0700 IronPort-SDR: wdOUR229PweJfZ6K+duQQjyzF7xFEGuxI8TT5EQsOo7a64xvcsf+hZPNJ8j5u9RuqMWO9kB63k 4U3KloOg5rNQ== X-IronPort-AV: E=Sophos;i="5.73,446,1583222400"; d="scan'208";a="443095230" Received: from unknown (HELO intel.com) ([10.237.72.89]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 May 2020 12:42:45 -0700 Date: Thu, 28 May 2020 22:38:52 +0300 From: "Lisovskiy, Stanislav" To: Ville Syrjala Message-ID: <20200528193852.GA24971@intel.com> References: <20200527200245.13184-1-ville.syrjala@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200527200245.13184-1-ville.syrjala@linux.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) Subject: Re: [Intel-gfx] [PATCH] drm/i915: Fix global state use-after-frees with a refcount 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: intel-gfx@lists.freedesktop.org Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, May 27, 2020 at 11:02:45PM +0300, Ville Syrjala wrote: > From: Ville Syrj=E4l=E4 > = > While the current locking/serialization of the global state > suffices for protecting the obj->state access and the actual > hardware reprogramming, we do have a problem with accessing > the old/new states during nonblocking commits. > = > The state computation and swap will be protected by the crtc > locks, but the commit_tails can finish out of order, thus also > causing the atomic states to be cleaned up out of order. This > would mean the commit that started first but finished last has > had its new state freed as the no-longer-needed old state by the > other commit. > = > To fix this let's just refcount the states. obj->state amounts > to one reference, and the intel_atomic_state holds extra references > to both its new and old global obj states. > = > Fixes: 0ef1905ecf2e ("drm/i915: Introduce better global state handling") > Signed-off-by: Ville Syrj=E4l=E4 > --- > .../gpu/drm/i915/display/intel_global_state.c | 45 ++++++++++++++++--- > .../gpu/drm/i915/display/intel_global_state.h | 3 ++ > 2 files changed, 42 insertions(+), 6 deletions(-) > = > diff --git a/drivers/gpu/drm/i915/display/intel_global_state.c b/drivers/= gpu/drm/i915/display/intel_global_state.c > index 212d4ee68205..7a19215ad844 100644 > --- a/drivers/gpu/drm/i915/display/intel_global_state.c > +++ b/drivers/gpu/drm/i915/display/intel_global_state.c > @@ -10,6 +10,28 @@ > #include "intel_display_types.h" > #include "intel_global_state.h" > = > +static void __intel_atomic_global_state_free(struct kref *kref) > +{ > + struct intel_global_state *obj_state =3D > + container_of(kref, struct intel_global_state, ref); > + struct intel_global_obj *obj =3D obj_state->obj; > + > + obj->funcs->atomic_destroy_state(obj, obj_state); > +} > + > +static void intel_atomic_global_state_put(struct intel_global_state *obj= _state) > +{ > + kref_put(&obj_state->ref, __intel_atomic_global_state_free); > +} > + > +static struct intel_global_state * > +intel_atomic_global_state_get(struct intel_global_state *obj_state) > +{ > + kref_get(&obj_state->ref); > + > + return obj_state; > +} > + > void intel_atomic_global_obj_init(struct drm_i915_private *dev_priv, > struct intel_global_obj *obj, > struct intel_global_state *state, > @@ -17,6 +39,10 @@ void intel_atomic_global_obj_init(struct drm_i915_priv= ate *dev_priv, > { > memset(obj, 0, sizeof(*obj)); > = > + state->obj =3D obj; > + > + kref_init(&state->ref); > + > obj->state =3D state; > obj->funcs =3D funcs; > list_add_tail(&obj->head, &dev_priv->global_obj_list); > @@ -28,7 +54,9 @@ void intel_atomic_global_obj_cleanup(struct drm_i915_pr= ivate *dev_priv) > = > list_for_each_entry_safe(obj, next, &dev_priv->global_obj_list, head) { > list_del(&obj->head); > - obj->funcs->atomic_destroy_state(obj, obj->state); > + > + drm_WARN_ON(&dev_priv->drm, kref_read(&obj->state->ref) !=3D 1); > + intel_atomic_global_state_put(obj->state); > } > } > = > @@ -97,10 +125,14 @@ intel_atomic_get_global_obj_state(struct intel_atomi= c_state *state, > if (!obj_state) > return ERR_PTR(-ENOMEM); > = > + obj_state->obj =3D obj; > obj_state->changed =3D false; > = > + kref_init(&obj_state->ref); > + > state->global_objs[index].state =3D obj_state; > - state->global_objs[index].old_state =3D obj->state; > + state->global_objs[index].old_state =3D > + intel_atomic_global_state_get(obj->state); > state->global_objs[index].new_state =3D obj_state; > state->global_objs[index].ptr =3D obj; > obj_state->state =3D state; > @@ -163,7 +195,9 @@ void intel_atomic_swap_global_state(struct intel_atom= ic_state *state) > new_obj_state->state =3D NULL; > = > state->global_objs[i].state =3D old_obj_state; > - obj->state =3D new_obj_state; > + > + intel_atomic_global_state_put(obj->state); > + obj->state =3D intel_atomic_global_state_get(new_obj_state); > } > } > = > @@ -172,10 +206,9 @@ void intel_atomic_clear_global_state(struct intel_at= omic_state *state) > int i; > = > for (i =3D 0; i < state->num_global_objs; i++) { > - struct intel_global_obj *obj =3D state->global_objs[i].ptr; > + intel_atomic_global_state_put(state->global_objs[i].old_state); > + intel_atomic_global_state_put(state->global_objs[i].new_state); Shouldn't we clean old_state only? = As I understand in absence of any transaction you now have a pool of global_obj each has a state with single kref taken. So when we are going to get a new state, we do +1 kref to old_state(which i= s current global obj->state) in order to prevent it being cleared by competing commit. However the new state doesn't have any kref taken by that moment. Then you swap do -1 kref for the old state and do +1 kref for new state, = which means that when you -1 kref again for old state in atomic_clear also, = it will be destroyed, however regarding the new state, as I understand it still has only single kref grabbed when it was swapped, = so isn't it going to be now removed? unless we are lucky and somebody haven't grabbed it already as an old_state in the next commit? Stan > = > - obj->funcs->atomic_destroy_state(obj, > - state->global_objs[i].state); > state->global_objs[i].ptr =3D NULL; > state->global_objs[i].state =3D NULL; > state->global_objs[i].old_state =3D NULL; > diff --git a/drivers/gpu/drm/i915/display/intel_global_state.h b/drivers/= gpu/drm/i915/display/intel_global_state.h > index e6163a469029..1f16fa3073c9 100644 > --- a/drivers/gpu/drm/i915/display/intel_global_state.h > +++ b/drivers/gpu/drm/i915/display/intel_global_state.h > @@ -6,6 +6,7 @@ > #ifndef __INTEL_GLOBAL_STATE_H__ > #define __INTEL_GLOBAL_STATE_H__ > = > +#include > #include > = > struct drm_i915_private; > @@ -54,7 +55,9 @@ struct intel_global_obj { > for_each_if(obj) > = > struct intel_global_state { > + struct intel_global_obj *obj; > struct intel_atomic_state *state; > + struct kref ref; > bool changed; > }; > = > -- = > 2.26.2 > = > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx