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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,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 24F85C43465 for ; Fri, 18 Sep 2020 02:17:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E729923718 for ; Fri, 18 Sep 2020 02:17:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600395429; bh=YamJ42CTzUXcA/68T8zl+RlfKuwzl6i79W3ajwGiu/k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=br9QuVc+/zD12nVMdJRleIttyjs4pn0KrPoDl7eEDTevxTrNaeF872L9Tlh7VJJWN sPFmmzNUnjW0ONn3lNXE/o6rniOOmzBaGuQ3DeqTfMx4c9v9dhVhywYPgw/DFwX0K/ +N3zPZHwDiceDWZaw08SpY0SazVbjCZBu5ePRzQ4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729521AbgIRCRJ (ORCPT ); Thu, 17 Sep 2020 22:17:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:47396 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729505AbgIRCRH (ORCPT ); Thu, 17 Sep 2020 22:17:07 -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 A271B235F7; Fri, 18 Sep 2020 02:17:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600395426; bh=YamJ42CTzUXcA/68T8zl+RlfKuwzl6i79W3ajwGiu/k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YhlujG3+NgMc7vMV6Io1WfzDetSz+cNRZODhJyLsHpU9fridSBEsi3BYl6rgMwoMj JWihU0+2N+QLwkRVvk3XNVEgGj/gqzvpWaXhNQyimJaHaFZw+oaQqRgJBAVqryNJlD CC2zDN78a/tFM+pOEiSlyd7FCuO+TkvDT24rPxFg= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Manish Mandlik , Marcel Holtmann , Sasha Levin , linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 20/64] Bluetooth: Fix refcount use-after-free issue Date: Thu, 17 Sep 2020 22:15:59 -0400 Message-Id: <20200918021643.2067895-20-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200918021643.2067895-1-sashal@kernel.org> References: <20200918021643.2067895-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Manish Mandlik [ Upstream commit 6c08fc896b60893c5d673764b0668015d76df462 ] There is no lock preventing both l2cap_sock_release() and chan->ops->close() from running at the same time. If we consider Thread A running l2cap_chan_timeout() and Thread B running l2cap_sock_release(), expected behavior is: A::l2cap_chan_timeout()->l2cap_chan_close()->l2cap_sock_teardown_cb() A::l2cap_chan_timeout()->l2cap_sock_close_cb()->l2cap_sock_kill() B::l2cap_sock_release()->sock_orphan() B::l2cap_sock_release()->l2cap_sock_kill() where, sock_orphan() clears "sk->sk_socket" and l2cap_sock_teardown_cb() marks socket as SOCK_ZAPPED. In l2cap_sock_kill(), there is an "if-statement" that checks if both sock_orphan() and sock_teardown() has been run i.e. sk->sk_socket is NULL and socket is marked as SOCK_ZAPPED. Socket is killed if the condition is satisfied. In the race condition, following occurs: A::l2cap_chan_timeout()->l2cap_chan_close()->l2cap_sock_teardown_cb() B::l2cap_sock_release()->sock_orphan() B::l2cap_sock_release()->l2cap_sock_kill() A::l2cap_chan_timeout()->l2cap_sock_close_cb()->l2cap_sock_kill() In this scenario, "if-statement" is true in both B::l2cap_sock_kill() and A::l2cap_sock_kill() and we hit "refcount: underflow; use-after-free" bug. Similar condition occurs at other places where teardown/sock_kill is happening: l2cap_disconnect_rsp()->l2cap_chan_del()->l2cap_sock_teardown_cb() l2cap_disconnect_rsp()->l2cap_sock_close_cb()->l2cap_sock_kill() l2cap_conn_del()->l2cap_chan_del()->l2cap_sock_teardown_cb() l2cap_conn_del()->l2cap_sock_close_cb()->l2cap_sock_kill() l2cap_disconnect_req()->l2cap_chan_del()->l2cap_sock_teardown_cb() l2cap_disconnect_req()->l2cap_sock_close_cb()->l2cap_sock_kill() l2cap_sock_cleanup_listen()->l2cap_chan_close()->l2cap_sock_teardown_cb() l2cap_sock_cleanup_listen()->l2cap_sock_kill() Protect teardown/sock_kill and orphan/sock_kill by adding hold_lock on l2cap channel to ensure that the socket is killed only after marked as zapped and orphan. Signed-off-by: Manish Mandlik Signed-off-by: Marcel Holtmann Signed-off-by: Sasha Levin --- net/bluetooth/l2cap_core.c | 26 +++++++++++++++----------- net/bluetooth/l2cap_sock.c | 16 +++++++++++++--- 2 files changed, 28 insertions(+), 14 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 0e31bbe1256cd..f6112f495a36c 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -403,6 +403,9 @@ static void l2cap_chan_timeout(struct work_struct *work) BT_DBG("chan %p state %s", chan, state_to_string(chan->state)); mutex_lock(&conn->chan_lock); + /* __set_chan_timer() calls l2cap_chan_hold(chan) while scheduling + * this work. No need to call l2cap_chan_hold(chan) here again. + */ l2cap_chan_lock(chan); if (chan->state == BT_CONNECTED || chan->state == BT_CONFIG) @@ -415,12 +418,12 @@ static void l2cap_chan_timeout(struct work_struct *work) l2cap_chan_close(chan, reason); - l2cap_chan_unlock(chan); - chan->ops->close(chan); - mutex_unlock(&conn->chan_lock); + l2cap_chan_unlock(chan); l2cap_chan_put(chan); + + mutex_unlock(&conn->chan_lock); } struct l2cap_chan *l2cap_chan_create(void) @@ -1714,9 +1717,9 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err) l2cap_chan_del(chan, err); - l2cap_chan_unlock(chan); - chan->ops->close(chan); + + l2cap_chan_unlock(chan); l2cap_chan_put(chan); } @@ -4316,6 +4319,7 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn, return 0; } + l2cap_chan_hold(chan); l2cap_chan_lock(chan); rsp.dcid = cpu_to_le16(chan->scid); @@ -4324,12 +4328,11 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn, chan->ops->set_shutdown(chan); - l2cap_chan_hold(chan); l2cap_chan_del(chan, ECONNRESET); - l2cap_chan_unlock(chan); - chan->ops->close(chan); + + l2cap_chan_unlock(chan); l2cap_chan_put(chan); mutex_unlock(&conn->chan_lock); @@ -4361,20 +4364,21 @@ static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn, return 0; } + l2cap_chan_hold(chan); l2cap_chan_lock(chan); if (chan->state != BT_DISCONN) { l2cap_chan_unlock(chan); + l2cap_chan_put(chan); mutex_unlock(&conn->chan_lock); return 0; } - l2cap_chan_hold(chan); l2cap_chan_del(chan, 0); - l2cap_chan_unlock(chan); - chan->ops->close(chan); + + l2cap_chan_unlock(chan); l2cap_chan_put(chan); mutex_unlock(&conn->chan_lock); diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index d9bbbded49ef8..cb024c25530a3 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1038,7 +1038,7 @@ done: } /* Kill socket (only if zapped and orphan) - * Must be called on unlocked socket. + * Must be called on unlocked socket, with l2cap channel lock. */ static void l2cap_sock_kill(struct sock *sk) { @@ -1199,8 +1199,15 @@ static int l2cap_sock_release(struct socket *sock) err = l2cap_sock_shutdown(sock, 2); + l2cap_chan_hold(l2cap_pi(sk)->chan); + l2cap_chan_lock(l2cap_pi(sk)->chan); + sock_orphan(sk); l2cap_sock_kill(sk); + + l2cap_chan_unlock(l2cap_pi(sk)->chan); + l2cap_chan_put(l2cap_pi(sk)->chan); + return err; } @@ -1218,12 +1225,15 @@ static void l2cap_sock_cleanup_listen(struct sock *parent) BT_DBG("child chan %p state %s", chan, state_to_string(chan->state)); + l2cap_chan_hold(chan); l2cap_chan_lock(chan); + __clear_chan_timer(chan); l2cap_chan_close(chan, ECONNRESET); - l2cap_chan_unlock(chan); - l2cap_sock_kill(sk); + + l2cap_chan_unlock(chan); + l2cap_chan_put(chan); } } -- 2.25.1