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 0D682C282CE for ; Wed, 24 Apr 2019 14:45:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0888218FC for ; Wed, 24 Apr 2019 14:44:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556117099; bh=vyG7Z8jDFeJbDgPAB1a8INh5VOpqKbMC5kfVSZ1tgrQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rhSgYRtMMsMkkXVhPtF28vzLOU8ejCketXEbZbOEzorBkqIcBjHvee0bdHZnGuW0/ v/Dk4gaBmGnYOM9G5iYLKDO3P1eSAuOAMT0Mp1nwVCk+v1vzwu9nguBJnBXhuVFPA1 15nNn6u1Gxm8/q6Lm1OMqGdJ+WlKMv2PR7C+Q6+M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732021AbfDXOo7 (ORCPT ); Wed, 24 Apr 2019 10:44:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:41862 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731695AbfDXOj3 (ORCPT ); Wed, 24 Apr 2019 10:39:29 -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 7DF8121900; Wed, 24 Apr 2019 14:39:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556116768; bh=vyG7Z8jDFeJbDgPAB1a8INh5VOpqKbMC5kfVSZ1tgrQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=x8mpdu6ZxpLM3Gl+rZgUoOUjhrcSnG/LooMu3JiY+VcYPH1DjFrI4ZzOKYDiVLwlX lCSiXlJnQyzBDtx0XPk7teybVBB1qOoyPRUELxFGgQxntM46IIgUS6XqVk7Y7peiIA YDCG7f9xy1oAn2321/apdoabZOdOr0NSJ1gejj1k= 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 07/52] batman-adv: Reduce tt_local hash refcnt only for removed entry Date: Wed, 24 Apr 2019 10:38:25 -0400 Message-Id: <20190424143911.28890-7-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 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 d21624c44665..696e6ddc534b 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -1332,9 +1332,10 @@ 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) @@ -1363,15 +1364,18 @@ 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