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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 344EBC4167E for ; Mon, 18 Apr 2022 14:08:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343898AbiDROIi (ORCPT ); Mon, 18 Apr 2022 10:08:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245361AbiDRNx1 (ORCPT ); Mon, 18 Apr 2022 09:53:27 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E5DD6583; Mon, 18 Apr 2022 06:02:40 -0700 (PDT) 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 5CF7660B70; Mon, 18 Apr 2022 13:02:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DBE1C385A8; Mon, 18 Apr 2022 13:02:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650286958; bh=j1ibkf07OPqJJuH+STE0U3Yp+RdmbtTkDExfewtsS1Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W1JH7E6Pf82vxD+tKdIkI6c5zSfGo5T03Zt0GCxAwvx0UNBE2MxSmswstxaUgGWSz +SEUn+0FJ5+e7v4/ZtA37ifdgGqjzvWswWGAPjRl4CYFdKSgIsQGWwjHLfLq6sVR8B zd88NTGaRMjzTD6bPUdZqtco7EOFcefzsgFSCJFk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, NeilBrown , Trond Myklebust Subject: [PATCH 4.9 015/218] SUNRPC: avoid race between mod_timer() and del_timer_sync() Date: Mon, 18 Apr 2022 14:11:21 +0200 Message-Id: <20220418121159.475432000@linuxfoundation.org> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220418121158.636999985@linuxfoundation.org> References: <20220418121158.636999985@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: NeilBrown commit 3848e96edf4788f772d83990022fa7023a233d83 upstream. xprt_destory() claims XPRT_LOCKED and then calls del_timer_sync(). Both xprt_unlock_connect() and xprt_release() call ->release_xprt() which drops XPRT_LOCKED and *then* xprt_schedule_autodisconnect() which calls mod_timer(). This may result in mod_timer() being called *after* del_timer_sync(). When this happens, the timer may fire long after the xprt has been freed, and run_timer_softirq() will probably crash. The pairing of ->release_xprt() and xprt_schedule_autodisconnect() is always called under ->transport_lock. So if we take ->transport_lock to call del_timer_sync(), we can be sure that mod_timer() will run first (if it runs at all). Cc: stable@vger.kernel.org Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xprt.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -1446,7 +1446,14 @@ static void xprt_destroy(struct rpc_xprt /* Exclude transport connect/disconnect handlers */ wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_UNINTERRUPTIBLE); + /* + * xprt_schedule_autodisconnect() can run after XPRT_LOCKED + * is cleared. We use ->transport_lock to ensure the mod_timer() + * can only run *before* del_time_sync(), never after. + */ + spin_lock(&xprt->transport_lock); del_timer_sync(&xprt->timer); + spin_unlock(&xprt->transport_lock); rpc_xprt_debugfs_unregister(xprt); rpc_destroy_wait_queue(&xprt->binding);