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[156.151.31.86]) by mx.google.com with ESMTPS id f13si1186057vsm.173.2019.06.26.09.31.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 Jun 2019 09:31:02 -0700 (PDT) Received-SPF: pass (google.com: domain of darrick.wong@oracle.com designates 156.151.31.86 as permitted sender) client-ip=156.151.31.86; Authentication-Results: mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2018-07-02 header.b="N/a93ebu"; spf=pass (google.com: domain of darrick.wong@oracle.com designates 156.151.31.86 as permitted sender) smtp.mailfrom=darrick.wong@oracle.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=oracle.com Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5QGU4Wg004218; Wed, 26 Jun 2019 16:30:39 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=Mz7em8B5BcTHywkzCrR8lugIdy2ootcWo4w3RRWBYaM=; b=N/a93ebuSSKM+1UIO0buPOjR9AvCbLsHhw01AwBMp/XW9BUb98JLnzoJbLgwOZFWmGyw hJdpkR7HkvPCAWlWLDnQsdQatbUdssqmn37SwPrTcAyE+/9x/iin4aJ6YtVFtP1GNmmr W4gQLbQG2SBcdOy5QNpDSE2/3fIVqQVrn7mZXub6KhldCj8Zzx/yQQ7a5EH7pzSZXmup IrJvp7zWK9kXgRoeoC8dGqS2tKAzLiR74Ta5S5LQWYLQBZWpbM10fUskgAys8/96vQdr G26RY/thy8CrA4lCa0mPtRoigi2YSG7nQksiKL4VCeGiPZV6yAFAimBMe+B5DQlWGUUd ig== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2130.oracle.com with ESMTP id 2t9brtbf85-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 26 Jun 2019 16:30:39 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5QGRxdd192423; Wed, 26 Jun 2019 16:28:38 GMT Received: from pps.reinject (localhost [127.0.0.1]) by aserp3020.oracle.com with ESMTP id 2t9p6uvctr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 26 Jun 2019 16:28:38 +0000 Received: from aserp3020.oracle.com (aserp3020.oracle.com [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x5QGScxQ193859; Wed, 26 Jun 2019 16:28:38 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 2t9p6uvctj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 26 Jun 2019 16:28:38 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x5QGSZWS032167; Wed, 26 Jun 2019 16:28:35 GMT Received: from localhost (/10.159.137.246) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 26 Jun 2019 09:28:35 -0700 Date: Wed, 26 Jun 2019 09:28:31 -0700 From: "Darrick J. Wong" To: Al Viro Cc: matthew.garrett@nebula.com, yuchao0@huawei.com, tytso@mit.edu, ard.biesheuvel@linaro.org, josef@toxicpanda.com, hch@infradead.org, clm@fb.com, adilger.kernel@dilger.ca, jack@suse.com, dsterba@suse.com, jaegeuk@kernel.org, jk@ozlabs.org, reiserfs-devel@vger.kernel.org, linux-efi@vger.kernel.org, devel@lists.orangefs.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-nilfs@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org Subject: Re: [PATCH 5/5] vfs: don't allow writes to swap files Message-ID: <20190626162831.GF5171@magnolia> References: <156151637248.2283603.8458727861336380714.stgit@magnolia> <156151641177.2283603.7806026378321236401.stgit@magnolia> <20190626035151.GA10613@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190626035151.GA10613@ZenIV.linux.org.uk> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9300 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906260193 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 26, 2019 at 04:51:51AM +0100, Al Viro wrote: > On Tue, Jun 25, 2019 at 07:33:31PM -0700, Darrick J. Wong wrote: > > --- a/fs/attr.c > > +++ b/fs/attr.c > > @@ -236,6 +236,9 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de > > if (IS_IMMUTABLE(inode)) > > return -EPERM; > > > > + if (IS_SWAPFILE(inode)) > > + return -ETXTBSY; > > + > > if ((ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) && > > IS_APPEND(inode)) > > return -EPERM; > > Er... So why exactly is e.g. chmod(2) forbidden for swapfiles? Or touch(1), > for that matter... Oops, that check is overly broad; I think the only attribute change we need to filter here is ATTR_SIZE.... which we could do unconditionally in inode_newsize_ok. What's the use case for allowing userspace to increase the size of an active swapfile? I don't see any; the kernel has a permanent lease on the file space mapping (at least until swapoff)... > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 596ac98051c5..1ca4ee8c2d60 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -3165,6 +3165,19 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > > if (error) > > goto bad_swap; > > > > + /* > > + * Flush any pending IO and dirty mappings before we start using this > > + * swap file. > > + */ > > + if (S_ISREG(inode->i_mode)) { > > + inode->i_flags |= S_SWAPFILE; > > + error = inode_drain_writes(inode); > > + if (error) { > > + inode->i_flags &= ~S_SWAPFILE; > > + goto bad_swap; > > + } > > + } > > Why are swap partitions any less worthy of protection? Hmm, yeah, S_SWAPFILE should apply to block devices too. I figured that the mantra of "sane tools will open block devices with O_EXCL" should have sufficed, but there's really no reason to allow that either. --D