From patchwork Fri Jan 15 23:58:16 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kamal Mostafa X-Patchwork-Id: 568730 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 45E2F140BB3; Sat, 16 Jan 2016 11:08:21 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1aKEPi-0006LD-6J; Sat, 16 Jan 2016 00:08:18 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1aKELP-0003Xu-Ev for kernel-team@lists.ubuntu.com; Sat, 16 Jan 2016 00:03:51 +0000 Received: from 1.general.kamal.us.vpn ([10.172.68.52] helo=fourier) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1aKELP-0007pv-2H; Sat, 16 Jan 2016 00:03:51 +0000 Received: from kamal by fourier with local (Exim 4.82) (envelope-from ) id 1aKELM-0001KB-8o; Fri, 15 Jan 2016 16:03:48 -0800 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH 4.2.y-ckt 082/305] mac80211: mesh: fix call_rcu() usage Date: Fri, 15 Jan 2016 15:58:16 -0800 Message-Id: <1452902519-2754-83-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1452902519-2754-1-git-send-email-kamal@canonical.com> References: <1452902519-2754-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Cc: Kamal Mostafa , Johannes Berg X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 4.2.8-ckt2 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Johannes Berg commit c2e703a55245bfff3db53b1f7cbe59f1ee8a4339 upstream. When using call_rcu(), the called function may be delayed quite significantly, and without a matching rcu_barrier() there's no way to be sure it has finished. Therefore, global state that could be gone/freed/reused should never be touched in the callback. Fix this in mesh by moving the atomic_dec() into the caller; that's not really a problem since we already unlinked the path and it will be destroyed anyway. This fixes a crash Jouni observed when running certain tests in a certain order, in which the mesh interface was torn down, the memory reused for a function pointer (work struct) and running that then crashed since the pointer had been decremented by 1, resulting in an invalid instruction byte stream. Fixes: eb2b9311fd00 ("mac80211: mesh path table implementation") Reported-by: Jouni Malinen Signed-off-by: Johannes Berg Signed-off-by: Kamal Mostafa --- net/mac80211/mesh_pathtbl.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c index b890e22..b3b44a5 100644 --- a/net/mac80211/mesh_pathtbl.c +++ b/net/mac80211/mesh_pathtbl.c @@ -779,10 +779,8 @@ void mesh_plink_broken(struct sta_info *sta) static void mesh_path_node_reclaim(struct rcu_head *rp) { struct mpath_node *node = container_of(rp, struct mpath_node, rcu); - struct ieee80211_sub_if_data *sdata = node->mpath->sdata; del_timer_sync(&node->mpath->timer); - atomic_dec(&sdata->u.mesh.mpaths); kfree(node->mpath); kfree(node); } @@ -790,8 +788,9 @@ static void mesh_path_node_reclaim(struct rcu_head *rp) /* needs to be called with the corresponding hashwlock taken */ static void __mesh_path_del(struct mesh_table *tbl, struct mpath_node *node) { - struct mesh_path *mpath; - mpath = node->mpath; + struct mesh_path *mpath = node->mpath; + struct ieee80211_sub_if_data *sdata = node->mpath->sdata; + spin_lock(&mpath->state_lock); mpath->flags |= MESH_PATH_RESOLVING; if (mpath->is_gate) @@ -799,6 +798,7 @@ static void __mesh_path_del(struct mesh_table *tbl, struct mpath_node *node) hlist_del_rcu(&node->list); call_rcu(&node->rcu, mesh_path_node_reclaim); spin_unlock(&mpath->state_lock); + atomic_dec(&sdata->u.mesh.mpaths); atomic_dec(&tbl->entries); }