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=-15.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 0A853C432C3 for ; Wed, 27 Nov 2019 04:24:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D033C2071E for ; Wed, 27 Nov 2019 04:24:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Uov/dvVa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727752AbfK0EYp (ORCPT ); Tue, 26 Nov 2019 23:24:45 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:41562 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727738AbfK0EYo (ORCPT ); Tue, 26 Nov 2019 23:24:44 -0500 Received: by mail-pf1-f195.google.com with SMTP id s18so1748077pfd.8 for ; Tue, 26 Nov 2019 20:24:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=cruZnOIQhNKwaUdTnpxXaRkPPQIJLlnQzi55bfc1FDk=; b=Uov/dvVa+NFZre/Pxa63oFagioekbzhykEY9uC1NgQlWTmDe3MrzWWvy9Zt7KnD6nx JcVzMDenZzT9Jy1ubkKHf4lG9QRkvegs3efFfrUdj94O6iXMUYwg7qGxuxwubrPMXHLh rOgkOXAbP2OWyoEm0pSD8uHT3ho5NZhpHXOX8Hwqi5J+clekJ8dcIy/v6pAwSwpQeoeo 9O8DofPw1gzKIJN0IpXwOxovlThNUTHxlGD/qdUnnlsoGJhuzCVHEhzFgFdVt3ljBxfV Fi4xdxIGx/VCFqVhmJLESMIFOZfA2bfnQmzo0CSx2RT5O7+HSjNXziEKEuP8qo4noLzf 45/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=cruZnOIQhNKwaUdTnpxXaRkPPQIJLlnQzi55bfc1FDk=; b=WkGcSkpAZo9rPV33tepkGO/kGVuIF557u1cUBZG43bYXKjSwgScxVlPnWlQR9HVdeg 37Ac2jL3/MCFxEv4KSauHbVDvHrOCPic4RYncSPWFYmNeGMiqpS+aapCUSDVQi4ZqbTg CcLegOBkvxi5fVFFdB6LGu7LE078vxyiyAxlyIMW+ZgbQsgMh56JaUgaB885OnAHbVl7 xTp9limlrTA1b2T2AhoCe0zhrhFwXChJIbFz93GOJV/K3F84Tz5/8bPF65hkJTxYMrai Zr3OQnvUVG9ZxdRWG9PvIuxD7K4+y2F3ZUoA6qfC3fsH8iMZ4OJTTlFLBiTHP5Z+kqkv Zs6g== X-Gm-Message-State: APjAAAV8v+d7Ei8BXkBVvNsqBRMzhWSZ2OX9jqlu5/y891DoAinQu8Xb P6lRgxBVEVEaHGBuMp/4tETKDQ== X-Google-Smtp-Source: APXvYqwHkLMzMxaDg4TQbnWaBd49ud789eb+LiQCmUKOjrQ+rDCkpU7IIi+KTGXAv9gUQiuoZeUrtw== X-Received: by 2002:a63:391:: with SMTP id 139mr2597363pgd.40.1574828682962; Tue, 26 Nov 2019 20:24:42 -0800 (PST) Received: from [100.112.92.218] ([104.133.9.106]) by smtp.gmail.com with ESMTPSA id e10sm4536872pfm.3.2019.11.26.20.24.42 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 26 Nov 2019 20:24:42 -0800 (PST) Date: Tue, 26 Nov 2019 20:24:32 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: yu kuai cc: hughd@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, yi.zhang@huawei.com, zhengbin13@huawei.com Subject: Re: [PATCH] mm/shmem.c: don't set 'seals' to 'F_SEAL_SEAL' in shmem_get_inode In-Reply-To: <20191127040051.39169-1-yukuai3@huawei.com> Message-ID: References: <20191127040051.39169-1-yukuai3@huawei.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 27 Nov 2019, yu kuai wrote: > 'seals' is set to 'F_SEAL_SEAL' in shmem_get_inode, which means "prevent > further seals from being set", thus sealing API will be useless and many > code in shmem.c will never be reached. For example: The sealing API is not useless, and that code can be reached. > > shmem_setattr > if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) || > (newsize > oldsize && (info->seals & F_SEAL_GROW))) > return -EPERM; > > So, initialize 'seals' to zero is more reasonable. > > Signed-off-by: yu kuai NAK. See memfd_create in mm/memfd.c (code which originated in mm/shmem.c, then was extended to support hugetlbfs also): sealing is for memfds, not for tmpfs or hugetlbfs files or SHM. Without thinking about it too hard, I believe that to allow sealing on tmpfs files would introduce surprising new behaviors on them, which might well raise security issues; and also be incompatible with the guarantees intended by sealing. > --- > mm/shmem.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 165fa6332993..7b032b347bda 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2256,7 +2256,6 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode > memset(info, 0, (char *)inode - (char *)info); > spin_lock_init(&info->lock); > atomic_set(&info->stop_eviction, 0); > - info->seals = F_SEAL_SEAL; > info->flags = flags & VM_NORESERVE; > INIT_LIST_HEAD(&info->shrinklist); > INIT_LIST_HEAD(&info->swaplist); > -- > 2.17.2