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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 48044C0650F for ; Thu, 8 Aug 2019 19:08:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C9F42173E for ; Thu, 8 Aug 2019 19:08:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565291302; bh=GO944Vpxi6hLaivkOV6+1MtsnIIXDbWFeObHenW4B/8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Pspg+uECHcxa0++YYeRk8gT8mej4Asqxg/YCIvD0PkbL0JrvukJJXp0pCma1Jymmb 781aaGj5moWwhTDheLzBmF3YrJK2Uxn6yQYwgb+33p1q8GdPreTy+AsJoCwJUwxo3j Zsg9SGoHzW4w5jIdyYAPvPpmY5ngR0IFAVE738T0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404886AbfHHTIU (ORCPT ); Thu, 8 Aug 2019 15:08:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:42350 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404866AbfHHTIS (ORCPT ); Thu, 8 Aug 2019 15:08:18 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 14137214C6; Thu, 8 Aug 2019 19:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565291297; bh=GO944Vpxi6hLaivkOV6+1MtsnIIXDbWFeObHenW4B/8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kMvixmqKajo1TdKFS4lawTp6OtVtUDKxnVXwLE2AiS+O9FNtiPkBXcbDcljji2L5v DYzICfUGcfP9+SO+7P7hByjGkl8x3MIzgEW7sju920GW6IVJLCoy7/Tg4HHoq5/IHG GiAWVKo2SrJ6nq5ED+R0H/E5T+IHTXB3eFpSpthk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dexuan Cui , Sunil Muthuswamy , "David S. Miller" Subject: [PATCH 5.2 46/56] hv_sock: Fix hang when a connection is closed Date: Thu, 8 Aug 2019 21:05:12 +0200 Message-Id: <20190808190455.008606190@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190808190452.867062037@linuxfoundation.org> References: <20190808190452.867062037@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dexuan Cui [ Upstream commit 8c7885e5690be9a27231ebebf82ef29fbf46c4e4 ] There is a race condition for an established connection that is being closed by the guest: the refcnt is 4 at the end of hvs_release() (Note: here the 'remove_sock' is false): 1 for the initial value; 1 for the sk being in the bound list; 1 for the sk being in the connected list; 1 for the delayed close_work. After hvs_release() finishes, __vsock_release() -> sock_put(sk) *may* decrease the refcnt to 3. Concurrently, hvs_close_connection() runs in another thread: calls vsock_remove_sock() to decrease the refcnt by 2; call sock_put() to decrease the refcnt to 0, and free the sk; next, the "release_sock(sk)" may hang due to use-after-free. In the above, after hvs_release() finishes, if hvs_close_connection() runs faster than "__vsock_release() -> sock_put(sk)", then there is not any issue, because at the beginning of hvs_close_connection(), the refcnt is still 4. The issue can be resolved if an extra reference is taken when the connection is established. Fixes: a9eeb998c28d ("hv_sock: Add support for delayed close") Signed-off-by: Dexuan Cui Reviewed-by: Sunil Muthuswamy Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/vmw_vsock/hyperv_transport.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/net/vmw_vsock/hyperv_transport.c +++ b/net/vmw_vsock/hyperv_transport.c @@ -311,6 +311,11 @@ static void hvs_close_connection(struct lock_sock(sk); hvs_do_close_lock_held(vsock_sk(sk), true); release_sock(sk); + + /* Release the refcnt for the channel that's opened in + * hvs_open_connection(). + */ + sock_put(sk); } static void hvs_open_connection(struct vmbus_channel *chan) @@ -378,6 +383,9 @@ static void hvs_open_connection(struct v } set_per_channel_state(chan, conn_from_host ? new : sk); + + /* This reference will be dropped by hvs_close_connection(). */ + sock_hold(conn_from_host ? new : sk); vmbus_set_chn_rescind_callback(chan, hvs_close_connection); /* Set the pending send size to max packet size to always get