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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,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 E3CBDC282CE for ; Wed, 24 Apr 2019 14:45:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE7F2218FC for ; Wed, 24 Apr 2019 14:45:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556117109; bh=AMYpGufnMLOUDzQX+7uAzUQTeVZQOfyT+F5WYikzXrA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Ly14qiSaEpx4wL9r6iTcVBypnFJkWcsoHHhjAYeHci3SWU/GzcGQNVvI0p/1hSRg/ KZ20mhkdKSNkKGeBSbo18u/Q4mZR7axS+jW7PUwZ637N2x4/JwPQiTgfilD53eVmVs IjrJ5OHhk/xcbgpc4KdCr8vh0vAPJ1KTzldWVV6s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732111AbfDXOpI (ORCPT ); Wed, 24 Apr 2019 10:45:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:41846 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731684AbfDXOj1 (ORCPT ); Wed, 24 Apr 2019 10:39:27 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7DE1C218FD; Wed, 24 Apr 2019 14:39:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556116766; bh=AMYpGufnMLOUDzQX+7uAzUQTeVZQOfyT+F5WYikzXrA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=swwlDFjRE7vYDmGASuMzbNg5Y3loolVM9u4BGztkmtEqIfQpDVrAZK5kyBltL/I9v QWhxAoa8bDzvOWOyaS51P8k5ApyJPYb667kKqRDWJSJFsEJ9ZEiHLmzGcZKqhQ4FSp PpPjtnqrJJ/W0lgoE5bUqWwFK2FTkO6yC04J9BA0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sven Eckelmann , Simon Wunderlich , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 06/52] batman-adv: Reduce claim hash refcnt only for removed entry Date: Wed, 24 Apr 2019 10:38:24 -0400 Message-Id: <20190424143911.28890-6-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190424143911.28890-1-sashal@kernel.org> References: <20190424143911.28890-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Sven Eckelmann [ Upstream commit 4ba104f468bbfc27362c393815d03aa18fb7a20f ] 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: Sasha Levin --- net/batman-adv/bridge_loop_avoidance.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c index 5f1aeeded0e3..85faf25c2912 100644 --- a/net/batman-adv/bridge_loop_avoidance.c +++ b/net/batman-adv/bridge_loop_avoidance.c @@ -803,6 +803,8 @@ static void batadv_bla_del_claim(struct batadv_priv *bat_priv, 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; @@ -813,10 +815,18 @@ static void batadv_bla_del_claim(struct batadv_priv *bat_priv, batadv_dbg(BATADV_DBG_BLA, bat_priv, "%s(): %pM, vid %d\n", __func__, mac, batadv_print_vid(vid)); - batadv_hash_remove(bat_priv->bla.claim_hash, batadv_compare_claim, - batadv_choose_claim, claim); - batadv_claim_put(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_put(claim_removed_entry); + +free_claim: /* don't need the reference from hash_find() anymore */ batadv_claim_put(claim); } -- 2.19.1