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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFC29C43217 for ; Thu, 13 Oct 2022 18:13:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231812AbiJMSNW (ORCPT ); Thu, 13 Oct 2022 14:13:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231769AbiJMSMa (ORCPT ); Thu, 13 Oct 2022 14:12:30 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5CBA3170DCC; Thu, 13 Oct 2022 11:09:19 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 003F2B820CB; Thu, 13 Oct 2022 18:02:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F70DC433C1; Thu, 13 Oct 2022 18:02:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1665684151; bh=cLMk1ar/nQON1mZgjjsdpVy1arXfNUVtd1FNGe7wHxc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Mg6F2PMgkRvjBgb7z6ZNUS4aU5aXRC+Rglz7+CORq8TFS29/6dw+IKg7sUwfP2c/Z /Ci0tHCvtu3u/s93mL3YBUkRd/Ww7LeuVCE0NiPH4sD00knBGUQei87+FwVRjCXN52 zxdMspKzaKmt/VlwLVDFYKm7g3B5R3xT0WvFONE0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, butt3rflyh4ck , Jeremy Kerr , "David S. Miller" Subject: [PATCH 6.0 30/34] mctp: prevent double key removal and unref Date: Thu, 13 Oct 2022 19:53:08 +0200 Message-Id: <20221013175147.291795983@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221013175146.507746257@linuxfoundation.org> References: <20221013175146.507746257@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jeremy Kerr commit 3a732b46736cd8a29092e4b0b1a9ba83e672bf89 upstream. Currently, we have a bug where a simultaneous DROPTAG ioctl and socket close may race, as we attempt to remove a key from lists twice, and perform an unref for each removal operation. This may result in a uaf when we attempt the second unref. This change fixes the race by making __mctp_key_remove tolerant to being called on a key that has already been removed from the socket/net lists, and only performs the unref when we do the actual remove. We also need to hold the list lock on the ioctl cleanup path. This fix is based on a bug report and comprehensive analysis from butt3rflyh4ck , found via syzkaller. Cc: stable@vger.kernel.org Fixes: 63ed1aab3d40 ("mctp: Add SIOCMCTP{ALLOC,DROP}TAG ioctls for tag control") Reported-by: butt3rflyh4ck Signed-off-by: Jeremy Kerr Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/mctp/af_mctp.c | 23 ++++++++++++++++------- net/mctp/route.c | 10 +++++----- 2 files changed, 21 insertions(+), 12 deletions(-) --- a/net/mctp/af_mctp.c +++ b/net/mctp/af_mctp.c @@ -295,11 +295,12 @@ __must_hold(&net->mctp.keys_lock) mctp_dev_release_key(key->dev, key); spin_unlock_irqrestore(&key->lock, flags); - hlist_del(&key->hlist); - hlist_del(&key->sklist); - - /* unref for the lists */ - mctp_key_unref(key); + if (!hlist_unhashed(&key->hlist)) { + hlist_del_init(&key->hlist); + hlist_del_init(&key->sklist); + /* unref for the lists */ + mctp_key_unref(key); + } kfree_skb(skb); } @@ -373,9 +374,17 @@ static int mctp_ioctl_alloctag(struct mc ctl.tag = tag | MCTP_TAG_OWNER | MCTP_TAG_PREALLOC; if (copy_to_user((void __user *)arg, &ctl, sizeof(ctl))) { - spin_lock_irqsave(&key->lock, flags); - __mctp_key_remove(key, net, flags, MCTP_TRACE_KEY_DROPPED); + unsigned long fl2; + /* Unwind our key allocation: the keys list lock needs to be + * taken before the individual key locks, and we need a valid + * flags value (fl2) to pass to __mctp_key_remove, hence the + * second spin_lock_irqsave() rather than a plain spin_lock(). + */ + spin_lock_irqsave(&net->mctp.keys_lock, flags); + spin_lock_irqsave(&key->lock, fl2); + __mctp_key_remove(key, net, fl2, MCTP_TRACE_KEY_DROPPED); mctp_key_unref(key); + spin_unlock_irqrestore(&net->mctp.keys_lock, flags); return -EFAULT; } --- a/net/mctp/route.c +++ b/net/mctp/route.c @@ -228,12 +228,12 @@ __releases(&key->lock) if (!key->manual_alloc) { spin_lock_irqsave(&net->mctp.keys_lock, flags); - hlist_del(&key->hlist); - hlist_del(&key->sklist); + if (!hlist_unhashed(&key->hlist)) { + hlist_del_init(&key->hlist); + hlist_del_init(&key->sklist); + mctp_key_unref(key); + } spin_unlock_irqrestore(&net->mctp.keys_lock, flags); - - /* unref for the lists */ - mctp_key_unref(key); } /* and one for the local reference */