From patchwork Sat Feb 23 14:09:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sven Eckelmann X-Patchwork-Id: 17837 X-Patchwork-Delegate: sw@simonwunderlich.de 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 72FF081BE2; Sat, 23 Feb 2019 15:09:43 +0100 (CET) Authentication-Results: open-mesh.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=narfation.org header.i=@narfation.org header.b="Iv/FiP0s"; dkim-atps=neutral Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=79.140.41.39; helo=v3-1039.vlinux.de; envelope-from=sven@narfation.org; receiver= Received: from v3-1039.vlinux.de (narfation.org [79.140.41.39]) by open-mesh.org (Postfix) with ESMTPS id 6EE7681BD4 for ; Sat, 23 Feb 2019 15:09:42 +0100 (CET) Received: from sven-desktop.home.narfation.org (p200300C5973408FD0000000000004065.dip0.t-ipconnect.de [IPv6:2003:c5:9734:8fd::4065]) by v3-1039.vlinux.de (Postfix) with ESMTPSA id 44B001100FB; Sat, 23 Feb 2019 15:09:40 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=narfation.org; s=20121; t=1550930980; bh=jBT89SFkAuPBqyNdXW6K1O5pw7d2Mfj4cvn235Fw2a8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Iv/FiP0sZy6Gh+4oyK4scN+qIwX9rOM+VoVvPJhPUX3WGpCpGfxxJ2hal2fdPuLVO SvEUMVZYB9RqSxpoABS+MFNCARt6BccvsYNuIV3A6JHNjygVzm5JWY1aF+cP80pB4K zkm3Hz5n2IlaPOSvkZIm7qrtynjqa1ljMv6XMgzY= From: Sven Eckelmann To: b.a.t.m.a.n@lists.open-mesh.org Date: Sat, 23 Feb 2019 15:09:06 +0100 Message-Id: <20190223140906.28979-3-sven@narfation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190223140906.28979-1-sven@narfation.org> References: <20190223140906.28979-1-sven@narfation.org> MIME-Version: 1.0 Subject: [B.A.T.M.A.N.] batman-adv: Reduce tt_global hash refcnt only for removed entry X-BeenThere: b.a.t.m.a.n@lists.open-mesh.org X-Mailman-Version: 2.1.23 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 Cc: Antonio Quartulli Errors-To: b.a.t.m.a.n-bounces@lists.open-mesh.org Sender: "B.A.T.M.A.N" The batadv_hash_remove is a function which searches the hashtable for an entry using a needle, a hashtable bucket selection function and a compare function. It will lock the bucket list and delete an entry when the compare function matches it with the needle. It returns the pointer to the hlist_node which matches or NULL when no entry matches the needle. The batadv_tt_global_free is not itself protected in anyway to avoid that any other function is modifying the hashtable between the search for the entry and the call to batadv_hash_remove. It can therefore happen that the entry either doesn't exist anymore or an entry was deleted which is not the same object as the needle. In such an situation, the reference counter (for the reference stored in the hashtable) must not be reduced for the needle. Instead the reference counter of the actually removed entry has to be reduced. Otherwise the reference counter will underflow and the object might be freed before all its references were dropped. The kref helpers reported this problem as: refcount_t: underflow; use-after-free. Fixes: 7bad46397eff ("batman-adv: protect the local and the global trans-tables with rcu") Reported-by: Martin Weinelt Signed-off-by: Sven Eckelmann Acked-by: Antonio Quartulli --- Cc: Antonio Quartulli diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index b5cfc5068a904d060dee1a1c6cb4b0177198e5d9..26c4e2493ddfbfdea26a9b45409821834010a913 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -616,14 +616,26 @@ static void batadv_tt_global_free(struct batadv_priv *bat_priv, struct batadv_tt_global_entry *tt_global, const char *message) { + struct batadv_tt_global_entry *tt_removed_entry; + struct hlist_node *tt_removed_node; + batadv_dbg(BATADV_DBG_TT, bat_priv, "Deleting global tt entry %pM (vid: %d): %s\n", tt_global->common.addr, batadv_print_vid(tt_global->common.vid), message); - batadv_hash_remove(bat_priv->tt.global_hash, batadv_compare_tt, - batadv_choose_tt, &tt_global->common); - batadv_tt_global_entry_put(tt_global); + tt_removed_node = batadv_hash_remove(bat_priv->tt.global_hash, + batadv_compare_tt, + batadv_choose_tt, + &tt_global->common); + if (!tt_removed_node) + return; + + /* drop reference of remove hash entry */ + tt_removed_entry = hlist_entry(tt_removed_node, + struct batadv_tt_global_entry, + common.hash_entry); + batadv_tt_global_entry_put(tt_removed_entry); } /** -- 2.20.1