From patchwork Sat Feb 23 14:09:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sven Eckelmann X-Patchwork-Id: 17836 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 70C6581589; Sat, 23 Feb 2019 15:09:36 +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="hXWNB+s3"; 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 BA1E0805DE for ; Sat, 23 Feb 2019 15:09:34 +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 54A311100FB; Sat, 23 Feb 2019 15:09:34 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=narfation.org; s=20121; t=1550930974; bh=EuEFrrlJrJ8Q/sbLW4LAhgmfPOVfzgpzkyfe73u7fXE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hXWNB+s3y7q9l5S97nmiQwuEQFMutZaWU5RtUgWi52//bGXRPe8wNif2qGJRfgNww yEfC+mYlQRjx4VayRq6I3zr06JWJZYHff9PhH5x7KnPfebHNSFkQB/T7RsWZIEX65+ FeRDleZyx7HaABZZvZaw5ZCiS13qenZEpqv2ol+c= From: Sven Eckelmann To: b.a.t.m.a.n@lists.open-mesh.org Date: Sat, 23 Feb 2019 15:09:05 +0100 Message-Id: <20190223140906.28979-2-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_local 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: Martin Weinelt , Marek Lindner 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_local_remove 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: af912d77181f ("batman-adv: protect tt_local_entry from concurrent delete events") Signed-off-by: Sven Eckelmann --- Cc: Marek Lindner diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index f73d79139ae79834a3e429fab82b7d55e8a373d5..b5cfc5068a904d060dee1a1c6cb4b0177198e5d9 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -1337,9 +1337,10 @@ u16 batadv_tt_local_remove(struct batadv_priv *bat_priv, const u8 *addr, unsigned short vid, const char *message, bool roaming) { + struct batadv_tt_local_entry *tt_removed_entry; struct batadv_tt_local_entry *tt_local_entry; u16 flags, curr_flags = BATADV_NO_FLAGS; - void *tt_entry_exists; + struct hlist_node *tt_removed_node; tt_local_entry = batadv_tt_local_hash_find(bat_priv, addr, vid); if (!tt_local_entry) @@ -1368,15 +1369,18 @@ u16 batadv_tt_local_remove(struct batadv_priv *bat_priv, const u8 *addr, */ batadv_tt_local_event(bat_priv, tt_local_entry, BATADV_TT_CLIENT_DEL); - tt_entry_exists = batadv_hash_remove(bat_priv->tt.local_hash, + tt_removed_node = batadv_hash_remove(bat_priv->tt.local_hash, batadv_compare_tt, batadv_choose_tt, &tt_local_entry->common); - if (!tt_entry_exists) + if (!tt_removed_node) goto out; - /* extra call to free the local tt entry */ - batadv_tt_local_entry_put(tt_local_entry); + /* drop reference of remove hash entry */ + tt_removed_entry = hlist_entry(tt_removed_node, + struct batadv_tt_local_entry, + common.hash_entry); + batadv_tt_local_entry_put(tt_removed_entry); out: if (tt_local_entry) -- 2.20.1