From patchwork Tue Apr 26 03:27:18 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Antonio Quartulli X-Patchwork-Id: 15973 Return-Path: X-Original-To: patchwork@open-mesh.org Delivered-To: patchwork@open-mesh.org Received: from open-mesh.org (localhost [IPv6:::1]) by open-mesh.org (Postfix) with ESMTP id 176B5822CB; Tue, 26 Apr 2016 05:28:40 +0200 (CEST) Authentication-Results: open-mesh.org; dmarc=none header.from=unstable.cc Received-SPF: Permerror (SPF Permanent Error: Two or more type TXT spf records found.) identity=mailfrom; client-ip=5.148.176.60; helo=s2.neomailbox.net; envelope-from=a@unstable.cc; receiver=b.a.t.m.a.n@lists.open-mesh.org Authentication-Results: open-mesh.org; dmarc=none header.from=unstable.cc Received: from s2.neomailbox.net (s2.neomailbox.net [5.148.176.60]) by open-mesh.org (Postfix) with ESMTPS id 4DD5E822BC for ; Tue, 26 Apr 2016 05:28:13 +0200 (CEST) From: Antonio Quartulli To: davem@davemloft.net Date: Tue, 26 Apr 2016 11:27:18 +0800 Message-Id: <1461641239-7097-5-git-send-email-a@unstable.cc> In-Reply-To: <1461641239-7097-1-git-send-email-a@unstable.cc> References: <1461641239-7097-1-git-send-email-a@unstable.cc> Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org, Antonio Quartulli , Marek Lindner Subject: [B.A.T.M.A.N.] [PATCH 4/5] batman-adv: Reduce refcnt of removed router when updating route X-BeenThere: b.a.t.m.a.n@lists.open-mesh.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: The list for a Better Approach To Mobile Ad-hoc Networking List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking Errors-To: b.a.t.m.a.n-bounces@lists.open-mesh.org Sender: "B.A.T.M.A.N" From: Sven Eckelmann _batadv_update_route rcu_derefences orig_ifinfo->router outside of a spinlock protected region to print some information messages to the debug log. But this pointer is not checked again when the new pointer is assigned in the spinlock protected region. Thus is can happen that the value of orig_ifinfo->router changed in the meantime and thus the reference counter of the wrong router gets reduced after the spinlock protected region. Just rcu_dereferencing the value of orig_ifinfo->router inside the spinlock protected region (which also set the new pointer) is enough to get the correct old router object. Fixes: e1a5382f978b ("batman-adv: Make orig_node->router an rcu protected pointer") Signed-off-by: Sven Eckelmann Signed-off-by: Marek Lindner Signed-off-by: Antonio Quartulli --- net/batman-adv/routing.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c index 4dd646a52f1a..b781bf753250 100644 --- a/net/batman-adv/routing.c +++ b/net/batman-adv/routing.c @@ -105,6 +105,15 @@ static void _batadv_update_route(struct batadv_priv *bat_priv, neigh_node = NULL; spin_lock_bh(&orig_node->neigh_list_lock); + /* curr_router used earlier may not be the current orig_ifinfo->router + * anymore because it was dereferenced outside of the neigh_list_lock + * protected region. After the new best neighbor has replace the current + * best neighbor the reference counter needs to decrease. Consequently, + * the code needs to ensure the curr_router variable contains a pointer + * to the replaced best neighbor. + */ + curr_router = rcu_dereference_protected(orig_ifinfo->router, true); + rcu_assign_pointer(orig_ifinfo->router, neigh_node); spin_unlock_bh(&orig_node->neigh_list_lock); batadv_orig_ifinfo_put(orig_ifinfo);