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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 A4B0CC49ED7 for ; Fri, 13 Sep 2019 13:10:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 786B12089F for ; Fri, 13 Sep 2019 13:10:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568380213; bh=eFOTFJwtAfNBqRCj+iWOaH/R8rthngrWfSDc49ovITY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=eViFrEqdDhZRqE/VVH4FpdA1UpgP2gWNwg5E9i9fXLGKyI68F1GA46Z+O7PH/d+7z NChDtKeRSe7GRjw+lCthDrNz6DWdRRbNm2YscZ8crMdMuWOxw3vCls21zHdtOU1zYT i6HN57bSgVCXgEXWL63Hjd1wdYObf+edyZtClWPs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388702AbfIMNKM (ORCPT ); Fri, 13 Sep 2019 09:10:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:34956 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388665AbfIMNKJ (ORCPT ); Fri, 13 Sep 2019 09:10:09 -0400 Received: from localhost (unknown [104.132.45.99]) (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 03892206BB; Fri, 13 Sep 2019 13:10:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568380208; bh=eFOTFJwtAfNBqRCj+iWOaH/R8rthngrWfSDc49ovITY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FEEUVhY2H3s4H5Tzi9DNwST7pkTUHKpxq/yd3RdyA7163qaZolVuc8YL7RKHK3lyL kakEMM4PvpOxm4ZjCV7IjAMo9T1DiXLMUgPYn995lxhGWRpWhsmPRfEq8LVhA0kZRy LFTDnyYWaHXOOMz9hS9Hkg/kbectH/mV3kYceWj0= 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" , Sasha Levin Subject: [PATCH 4.14 14/21] hv_sock: Fix hang when a connection is closed Date: Fri, 13 Sep 2019 14:07:07 +0100 Message-Id: <20190913130507.116698849@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190913130501.285837292@linuxfoundation.org> References: <20190913130501.285837292@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 [ Upstream commit 685703b497bacea8765bb409d6b73455b73c540e ] 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: Sasha Levin --- net/vmw_vsock/hyperv_transport.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c index 52ac3e49c7efd..ec72a5edaa1b8 100644 --- a/net/vmw_vsock/hyperv_transport.c +++ b/net/vmw_vsock/hyperv_transport.c @@ -320,6 +320,11 @@ static void hvs_close_connection(struct vmbus_channel *chan) 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) @@ -389,6 +394,9 @@ static void hvs_open_connection(struct vmbus_channel *chan) } 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 -- 2.20.1