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=-9.8 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,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 BBF18C33CA3 for ; Sat, 11 Jan 2020 10:00:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 927752077C for ; Sat, 11 Jan 2020 10:00:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578736823; bh=NfbA8pO07EswMY0SuPWfahwVm7jF59HzRXEitD+Noqg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=F9vHvf7SSAe8icI73uFhddxq/sd0BR8fR/Uh66jcYkJZeoNLzvEPHa7KnTeca5s2k gSLrETBvoKc3MBAhbzrQHNc2CcMVAHwZtjb71ueeKppPVOGXry5WtOIbZn1M5AT4AF Uk9aNMLnd3Hit6yIK94uqD42fi3niOl7SUFM3CFs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729418AbgAKKAM (ORCPT ); Sat, 11 Jan 2020 05:00:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:55840 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729388AbgAKKAH (ORCPT ); Sat, 11 Jan 2020 05:00:07 -0500 Received: from localhost (unknown [62.119.166.9]) (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 A8CAB2082E; Sat, 11 Jan 2020 10:00:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578736807; bh=NfbA8pO07EswMY0SuPWfahwVm7jF59HzRXEitD+Noqg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RzMvGXo8/rZRc9RQJjnXp+8JSvvazDOoZgv1Q40tnAITjNXvK2c1N39REXuGRyFhb mU34+0/P7wDrrZQ+bocLLUxvlX3sk7rjykHPQr98Wmr+g9U2Z33IoRt6/CYjHsAh+9 WgLNRlrQ9vlA+pSB6k+OlwTqH9uOknGYHvKydOdc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Durrant , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Juergen Gross , Sasha Levin Subject: [PATCH 4.9 12/91] xen-blkback: prevent premature module unload Date: Sat, 11 Jan 2020 10:49:05 +0100 Message-Id: <20200111094847.475565864@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200111094844.748507863@linuxfoundation.org> References: <20200111094844.748507863@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: Paul Durrant [ Upstream commit fa2ac657f9783f0891b2935490afe9a7fd29d3fa ] Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem cache. This cache is destoyed when xen-blkif is unloaded so it is necessary to wait for the deferred free routine used for such objects to complete. This necessity was missed in commit 14855954f636 "xen-blkback: allow module to be cleanly unloaded". This patch fixes the problem by taking/releasing extra module references in xen_blkif_alloc/free() respectively. Signed-off-by: Paul Durrant Reviewed-by: Roger Pau Monné Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin --- drivers/block/xen-blkback/xenbus.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index ad736d7de838..1d1f86657967 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -178,6 +178,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) blkif->domid = domid; atomic_set(&blkif->refcnt, 1); init_completion(&blkif->drain_complete); + + /* + * Because freeing back to the cache may be deferred, it is not + * safe to unload the module (and hence destroy the cache) until + * this has completed. To prevent premature unloading, take an + * extra module reference here and release only when the object + * has been freed back to the cache. + */ + __module_get(THIS_MODULE); INIT_WORK(&blkif->free_work, xen_blkif_deferred_free); return blkif; @@ -322,6 +331,7 @@ static void xen_blkif_free(struct xen_blkif *blkif) /* Make sure everything is drained before shutting down */ kmem_cache_free(xen_blkif_cachep, blkif); + module_put(THIS_MODULE); } int __init xen_blkif_interface_init(void) -- 2.20.1