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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 1B1DFC433DF for ; Mon, 1 Jun 2020 12:31:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD47F2077D for ; Mon, 1 Jun 2020 12:31:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QBoWaP2e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726825AbgFAMbg (ORCPT ); Mon, 1 Jun 2020 08:31:36 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:29694 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726125AbgFAMbf (ORCPT ); Mon, 1 Jun 2020 08:31:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591014694; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0VOACdA2Kaw77MK1p6SFJPm5uM6Jc6RhnwZNlhKvqlk=; b=QBoWaP2eRHryUGBwHtZqv+Tb0e8iKNM5+hD4Tror1LmLnF3P7DAsaVHwQMw8boSLxu7cMT 4yGxOD1Ov8R2C8rXQP1WYVMcbzloq9COjwPqlDv8n/JLRfZbMeRkRucllJJgaXHOH65mWZ ru/pf+Rs6TBJVZSjwkyYYoTt1WJ4vnE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-360-VxsYkypcM6-zac2MMITW0A-1; Mon, 01 Jun 2020 08:31:32 -0400 X-MC-Unique: VxsYkypcM6-zac2MMITW0A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 45F4F107ACF2; Mon, 1 Jun 2020 12:31:31 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-112-138.rdu2.redhat.com [10.10.112.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3DBBF7E7E1; Mon, 1 Jun 2020 12:31:30 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20200601092150.3798343-1-chengzhihao1@huawei.com> References: <20200601092150.3798343-1-chengzhihao1@huawei.com> To: Zhihao Cheng Cc: dhowells@redhat.com, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com Subject: Re: [PATCH] afs: Fix memory leak in afs_put_sysnames() MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1306173.1591014689.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Mon, 01 Jun 2020 13:31:29 +0100 Message-ID: <1306174.1591014689@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Zhihao Cheng wrote: > sysnames should be freed after refcnt being decreased to zero in > afs_put_sysnames(). Good catch. > Besides, it would be better set net->sysnames to 'NULL' after net->sysna= mes > being released if afs_put_sysnames() aims on an afs_sysnames object. Why? We don't normally clear pointers when cleaning up a struct - and of = the two places this is relevant, in one we fail to set up a namespace and in t= he other we're tearing down a namespace. In neither case should the pointer = be accessed again. > @@ -894,7 +894,7 @@ static struct dentry *afs_lookup_atsys(struct inode = *dir, struct dentry *dentry, > */ > ret =3D NULL; > out_s: > - afs_put_sysnames(subs); > + afs_put_sysnames_and_null(net); This is definitely wrong. We obtained a ref 23 lines above and dropped th= e lock: read_lock(&net->sysnames_lock); subs =3D net->sysnames; refcount_inc(&subs->usage); read_unlock(&net->sysnames_lock); We are dropping *that* ref, not the one in the struct. Just adding the missing kfree() call into afs_put_sysnames() should suffic= e, thanks. David