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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 DEF50C4332B for ; Thu, 19 Mar 2020 13:36:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B761720787 for ; Thu, 19 Mar 2020 13:36:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584624997; bh=XdIXxjQE02hUwbTN4cGVTEPpCkxy4dyeETmIeQqK4j8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=vepjBMRkQ3Vj9guRdRmhK90QbA2wMLFSVmtxICyJqKQx922EZRTfFOYN1iE8lvuMN x2XBU9S4P8B6ty0zfAQ2UP6BwHN2hf/oLU2ahrS1+3+/4IYR8g6BIdDVj2oYuxRXo/ TogjKBGsrB85paAJ2nOLAE+szPi5agi8BaOta/8k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728366AbgCSNJj (ORCPT ); Thu, 19 Mar 2020 09:09:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:54056 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727775AbgCSNJd (ORCPT ); Thu, 19 Mar 2020 09:09:33 -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 A47DE214D8; Thu, 19 Mar 2020 13:09:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584623373; bh=XdIXxjQE02hUwbTN4cGVTEPpCkxy4dyeETmIeQqK4j8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VGR1QXU6fhVzhsH2agQbl6Py/J85L9yTm0LyuMeT5g8F7gmPOnXZ5k2lmlbxYTEkB UBj3Xhb9OYR8hcMpKbCXSOxZboTZgRUaFnu/KhYA9ZRqjMXxK70aOEOUEiZX9Fcu9L GPQik3NTP93IbsOLaTfgY/qW9yl65N9FF/qM/e2o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Sven Eckelmann , Simon Wunderlich Subject: [PATCH 4.4 81/93] batman-adv: Reduce tt_local hash refcnt only for removed entry Date: Thu, 19 Mar 2020 14:00:25 +0100 Message-Id: <20200319123950.223234871@linuxfoundation.org> X-Mailer: git-send-email 2.25.2 In-Reply-To: <20200319123924.795019515@linuxfoundation.org> References: <20200319123924.795019515@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 From: Sven Eckelmann commit 3d65b9accab4a7ed5038f6df403fbd5e298398c7 upstream. 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: Greg Kroah-Hartman --- net/batman-adv/translation-table.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -1049,9 +1049,10 @@ u16 batadv_tt_local_remove(struct batadv 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) @@ -1080,15 +1081,18 @@ u16 batadv_tt_local_remove(struct batadv */ 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_free_ref(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_free_ref(tt_removed_entry); out: if (tt_local_entry)