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 C8F3EC282E1 for ; Wed, 24 Apr 2019 14:59:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 921DF20878 for ; Wed, 24 Apr 2019 14:59:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556117961; bh=GAGYc+RBNY9gOAJBpGm59XaP147pRa+hODvmHtt6geU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=hykTbwGos5xGCaRKHHnWhjD7C4I+tGUDt/cN1B9tCfo7W28VWngqu9Gqwy4rginn5 cHgoSzFwtz1PqY7FMExryUeQ4qT+Ds+R1hMPsLic8zT2MwMR9SPdX1ZdkjMGDZPtDb SE/Gvsizbk+FzCGiZUzm4bDdd+w4+5kl2pHbZXm0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732570AbfDXO7U (ORCPT ); Wed, 24 Apr 2019 10:59:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:47030 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731324AbfDXOrX (ORCPT ); Wed, 24 Apr 2019 10:47:23 -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 8C44221900; Wed, 24 Apr 2019 14:47:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556117242; bh=GAGYc+RBNY9gOAJBpGm59XaP147pRa+hODvmHtt6geU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UgODOp2bDzSrMq8G6Cg/mm8lwFnHck6uh8xbrxiOLw8f5E2/4AhxLtQsjAZCb86A+ WnhrhUuXM2Da8g0/14w478Eqb7JJFPZ1eSU0cxzsEcG3E5QbPXNqEHSrdSN032feOV Tt3LDxI3TBiIxKwEPQKPVLe1MgW+x7FNcZQ35a74= 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 4.14 05/35] batman-adv: Reduce tt_local hash refcnt only for removed entry Date: Wed, 24 Apr 2019 10:46:39 -0400 Message-Id: <20190424144709.30215-5-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190424144709.30215-1-sashal@kernel.org> References: <20190424144709.30215-1-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 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 9da3455847ff..6c3e446abeed 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -1313,9 +1313,10 @@ 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) @@ -1344,15 +1345,18 @@ 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) -- 2.19.1