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 5B383C4332B for ; Thu, 19 Mar 2020 13:09:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DA34208D6 for ; Thu, 19 Mar 2020 13:09:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584623375; bh=eubgEQiBZwVdc6+E2bfCM0l6cQ4Eh9EROaluQ882r7s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wHoyojMSAnxdK7JiLksplJC/8TrOdWcZgQ2tS0RPjGh54Eclptnzu+4v4GM5J9VCS gq6LUvrYc8WQkqm+VgRfFFuldQXwrKKtq48FGEGXteZcv3bQTscp99LPz4qq+z1MsZ b9f4V3kq4Y1UggojZDhT3a8JcPoI+6GBtY4cS4uM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728354AbgCSNJd (ORCPT ); Thu, 19 Mar 2020 09:09:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:53976 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727557AbgCSNJb (ORCPT ); Thu, 19 Mar 2020 09:09:31 -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 2AE1420789; Thu, 19 Mar 2020 13:09:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584623370; bh=eubgEQiBZwVdc6+E2bfCM0l6cQ4Eh9EROaluQ882r7s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AjJHVBVXw0nlWOrrhT9dze0UCF0MdLwQmdwMpRHaLg2tvceYIJeO4o/hsks8wX2b3 Xplh4Gjf9PJA8sP+rh+qKZJUtEQWblcc5PKb1r2vxE80lJ7CxVbsI3BIA9eDExFdwC Mj6o3X5cZu7mdVd76OIbDryckLsqdFw8lfoPJYn4= 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 80/93] batman-adv: Reduce claim hash refcnt only for removed entry Date: Thu, 19 Mar 2020 14:00:24 +0100 Message-Id: <20200319123949.968334750@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 4ba104f468bbfc27362c393815d03aa18fb7a20f 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_bla_del_claim 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: 23721387c409 ("batman-adv: add basic bridge loop avoidance code") Signed-off-by: Sven Eckelmann Signed-off-by: Simon Wunderlich Signed-off-by: Greg Kroah-Hartman --- net/batman-adv/bridge_loop_avoidance.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) --- a/net/batman-adv/bridge_loop_avoidance.c +++ b/net/batman-adv/bridge_loop_avoidance.c @@ -694,6 +694,8 @@ static void batadv_bla_del_claim(struct const u8 *mac, const unsigned short vid) { struct batadv_bla_claim search_claim, *claim; + struct batadv_bla_claim *claim_removed_entry; + struct hlist_node *claim_removed_node; ether_addr_copy(search_claim.addr, mac); search_claim.vid = vid; @@ -704,10 +706,18 @@ static void batadv_bla_del_claim(struct batadv_dbg(BATADV_DBG_BLA, bat_priv, "bla_del_claim(): %pM, vid %d\n", mac, BATADV_PRINT_VID(vid)); - batadv_hash_remove(bat_priv->bla.claim_hash, batadv_compare_claim, - batadv_choose_claim, claim); - batadv_claim_free_ref(claim); /* reference from the hash is gone */ + claim_removed_node = batadv_hash_remove(bat_priv->bla.claim_hash, + batadv_compare_claim, + batadv_choose_claim, claim); + if (!claim_removed_node) + goto free_claim; + /* reference from the hash is gone */ + claim_removed_entry = hlist_entry(claim_removed_node, + struct batadv_bla_claim, hash_entry); + batadv_claim_free_ref(claim_removed_entry); + +free_claim: /* don't need the reference from hash_find() anymore */ batadv_claim_free_ref(claim); }