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=-8.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_GIT 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 78E0DC04A6B for ; Mon, 6 May 2019 14:48:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A7DA214AF for ; Mon, 6 May 2019 14:48:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557154094; bh=ZtmSWNbrhTQes5RcFE2KH2Zt7tti+iIeNVCZzV6kv2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Xk6RD4NZIAgTM6QpAMHfeAZ+ew7e13uVswCG/+8Nxi5w7K1aJK7QUyn3Dmnj8FkUe Hv9jC7txoVQyKEIZi+yXcJjbfw6ky5/EucFKTxo1DhR3shaZTw74KLUiOBF97RSYMo aB+OukGwyzrWcCaMRudn7pz6RBsPXXvhi1pO3r8I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729416AbfEFOsN (ORCPT ); Mon, 6 May 2019 10:48:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:48188 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728509AbfEFOsK (ORCPT ); Mon, 6 May 2019 10:48:10 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 91D4E2053B; Mon, 6 May 2019 14:48:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557154090; bh=ZtmSWNbrhTQes5RcFE2KH2Zt7tti+iIeNVCZzV6kv2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ItDVw2H0rIAs7bA6hWU26jPT+0A6Ggj2059UZdyb4lHr3Px47lJlfG8qojflZ0Oy0 HsVrsIgthuh0AM1z0pTLjwS9dxryQL47C/tNxyu+AVjlf6XxVMk9B4Y++8k2nk3fp9 FrQmVC6Ahes8oT3P3OAXcZt0ip1d8ZfXJ3DzArRA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sven Eckelmann , Simon Wunderlich , Sasha Levin Subject: [PATCH 4.9 32/62] batman-adv: Reduce tt_local hash refcnt only for removed entry Date: Mon, 6 May 2019 16:33:03 +0200 Message-Id: <20190506143053.845732740@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190506143051.102535767@linuxfoundation.org> References: <20190506143051.102535767@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit 3d65b9accab4a7ed5038f6df403fbd5e298398c7 ] 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: ef72706a0543 ("batman-adv: protect tt_local_entry from concurrent delete events") Signed-off-by: Sven Eckelmann Signed-off-by: Simon Wunderlich Signed-off-by: Sasha Levin --- net/batman-adv/translation-table.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index b9f9a310eb78..4f18fcd2d3c0 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -1308,9 +1308,10 @@ 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) @@ -1339,15 +1340,18 @@ 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