From patchwork Mon Feb 21 08:49:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 545029 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 9F11BC433EF for ; Mon, 21 Feb 2022 08:51:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344881AbiBUIvg (ORCPT ); Mon, 21 Feb 2022 03:51:36 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:41572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344876AbiBUIve (ORCPT ); Mon, 21 Feb 2022 03:51:34 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F21DC2BCB; Mon, 21 Feb 2022 00:51:11 -0800 (PST) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 8FD4C61132; Mon, 21 Feb 2022 08:51:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 738DEC340E9; Mon, 21 Feb 2022 08:51:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1645433471; bh=/hVOJlsFWLKRbsZ0LCXQz1BHsIWJgYUIFS3HbLPfFkY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ExED1Hb3Ma2O8c8wBlaHVAWABDKAIQdkVll3OF21Emk4XZvHUC3rr8ZTl/GSLul7R p+NyuYTu9u7Tgcx+FOqjdtcCjMpwq8NAB6GxT/VDYmzAcmP1Ut7ANaM+BbKP9SNK+I 14Oh/A5ws1v3eavRkQ4Ob0MYIt/xhJmIjo1NnOXA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Duoming Zhou , "David S. Miller" , Sasha Levin Subject: [PATCH 4.9 11/33] ax25: improve the incomplete fix to avoid UAF and NPD bugs Date: Mon, 21 Feb 2022 09:49:04 +0100 Message-Id: <20220221084908.924052016@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220221084908.568970525@linuxfoundation.org> References: <20220221084908.568970525@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Duoming Zhou [ Upstream commit 4e0f718daf97d47cf7dec122da1be970f145c809 ] The previous commit 1ade48d0c27d ("ax25: NPD bug when detaching AX25 device") introduce lock_sock() into ax25_kill_by_device to prevent NPD bug. But the concurrency NPD or UAF bug will occur, when lock_sock() or release_sock() dereferences the ax25_cb->sock. The NULL pointer dereference bug can be shown as below: ax25_kill_by_device() | ax25_release() | ax25_destroy_socket() | ax25_cb_del() ... | ... | ax25->sk=NULL; lock_sock(s->sk); //(1) | s->ax25_dev = NULL; | ... release_sock(s->sk); //(2) | ... | The root cause is that the sock is set to null before dereference site (1) or (2). Therefore, this patch extracts the ax25_cb->sock in advance, and uses ax25_list_lock to protect it, which can synchronize with ax25_cb_del() and ensure the value of sock is not null before dereference sites. The concurrency UAF bug can be shown as below: ax25_kill_by_device() | ax25_release() | ax25_destroy_socket() ... | ... | sock_put(sk); //FREE lock_sock(s->sk); //(1) | s->ax25_dev = NULL; | ... release_sock(s->sk); //(2) | ... | The root cause is that the sock is released before dereference site (1) or (2). Therefore, this patch uses sock_hold() to increase the refcount of sock and uses ax25_list_lock to protect it, which can synchronize with ax25_cb_del() in ax25_destroy_socket() and ensure the sock wil not be released before dereference sites. Signed-off-by: Duoming Zhou Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ax25/af_ax25.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index f4c8567e91b38..c4ef1be59cb19 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -80,6 +80,7 @@ static void ax25_kill_by_device(struct net_device *dev) { ax25_dev *ax25_dev; ax25_cb *s; + struct sock *sk; if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) return; @@ -88,13 +89,15 @@ static void ax25_kill_by_device(struct net_device *dev) again: ax25_for_each(s, &ax25_list) { if (s->ax25_dev == ax25_dev) { + sk = s->sk; + sock_hold(sk); spin_unlock_bh(&ax25_list_lock); - lock_sock(s->sk); + lock_sock(sk); s->ax25_dev = NULL; - release_sock(s->sk); + release_sock(sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock); - + sock_put(sk); /* The entry could have been deleted from the * list meanwhile and thus the next pointer is * no longer valid. Play it safe and restart