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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 1374DC43331 for ; Thu, 2 Apr 2020 17:32:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B113E20737 for ; Thu, 2 Apr 2020 17:32:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585848732; bh=l54tq96j/nSc6f5GJPAzzGOPS0gEBw9QHmPFWfAfs1E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aJXe5RAIsm0Xo2G+9+qbRZiYM0/kzqe8XVf4INEkWNzRo+5aWc8Er4RBHCFlFVG9c AarKhM21Dj5hMy+O6mIshC7Qu3BzvG2sACCiidifLyAjpytDpWvt8aRzvpmaGCia2D kY6rc4NV04Eecv8mGTho28KQVoxle8d3yfrS6r4c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389891AbgDBRcI (ORCPT ); Thu, 2 Apr 2020 13:32:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:32814 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389279AbgDBRcI (ORCPT ); Thu, 2 Apr 2020 13:32:08 -0400 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 B60F120737; Thu, 2 Apr 2020 17:32:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585848728; bh=l54tq96j/nSc6f5GJPAzzGOPS0gEBw9QHmPFWfAfs1E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=idwy5N3jUu9tdPAsx8pNxI34Fb9S85DRpwNJpI1gKSS2bg6SydBI+fgWmw2zMfWdX UfMUbloeKUqBC2ET8uptnWRYdw5ZubCTJg2i5DqoMSWWwimgxTwanEOa3s80Mu//Ok Uy9rB4M7+ptkCBjLNlKqtG3TuAmeEGheXgmjCrAQ= From: Will Deacon To: gregkh@linuxfoundation.org Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com, g.nault@alphalink.fr, "David S . Miller" , Will Deacon Subject: [PATCH 2/2] l2tp: fix race between l2tp_session_delete() and l2tp_tunnel_closeall() Date: Thu, 2 Apr 2020 18:31:58 +0100 Message-Id: <20200402173158.7798-3-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200402173158.7798-1-will@kernel.org> References: <20200402173158.7798-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Guillaume Nault commit b228a94066406b6c456321d69643b0d7ce11cfa6 upstream. There are several ways to remove L2TP sessions: * deleting a session explicitly using the netlink interface (with L2TP_CMD_SESSION_DELETE), * deleting the session's parent tunnel (either by closing the tunnel's file descriptor or using the netlink interface), * closing the PPPOL2TP file descriptor of a PPP pseudo-wire. In some cases, when these methods are used concurrently on the same session, the session can be removed twice, leading to use-after-free bugs. This patch adds a 'dead' flag, used by l2tp_session_delete() and l2tp_tunnel_closeall() to prevent them from stepping on each other's toes. The session deletion path used when closing a PPPOL2TP file descriptor doesn't need to be adapted. It already has to ensure that a session remains valid for the lifetime of its PPPOL2TP file descriptor. So it takes an extra reference on the session in the ->session_close() callback (pppol2tp_session_close()), which is eventually dropped in the ->sk_destruct() callback of the PPPOL2TP socket (pppol2tp_session_destruct()). Still, __l2tp_session_unhash() and l2tp_session_queue_purge() can be called twice and even concurrently for a given session, but thanks to proper locking and re-initialisation of list fields, this is not an issue. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller Signed-off-by: Will Deacon --- net/l2tp/l2tp_core.c | 6 ++++++ net/l2tp/l2tp_core.h | 1 + 2 files changed, 7 insertions(+) diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index 394a1ddb0782..7c3da29fad8e 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1351,6 +1351,9 @@ void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel) hlist_del_init(&session->hlist); + if (test_and_set_bit(0, &session->dead)) + goto again; + if (session->ref != NULL) (*session->ref)(session); @@ -1799,6 +1802,9 @@ EXPORT_SYMBOL_GPL(__l2tp_session_unhash); */ int l2tp_session_delete(struct l2tp_session *session) { + if (test_and_set_bit(0, &session->dead)) + return 0; + if (session->ref) (*session->ref)(session); __l2tp_session_unhash(session); diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h index 7cc49715606e..7c2037184b6c 100644 --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -84,6 +84,7 @@ struct l2tp_session_cfg { struct l2tp_session { int magic; /* should be * L2TP_SESSION_MAGIC */ + long dead; struct l2tp_tunnel *tunnel; /* back pointer to tunnel * context */ -- 2.26.0.rc2.310.g2932bb562d-goog