Return-Path: Received: from mail-ua1-f66.google.com ([209.85.222.66]:42108 "EHLO mail-ua1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726227AbeJMD4m (ORCPT ); Fri, 12 Oct 2018 23:56:42 -0400 MIME-Version: 1.0 References: <153923113649.5546.9840926895953408273.stgit@magnolia> <153923117420.5546.13317703807467393934.stgit@magnolia> In-Reply-To: <153923117420.5546.13317703807467393934.stgit@magnolia> Reply-To: fdmanana@gmail.com From: Filipe Manana Date: Fri, 12 Oct 2018 21:22:18 +0100 Message-ID: Subject: Re: [PATCH 05/25] vfs: avoid problematic remapping requests into partial EOF block To: "Darrick J. Wong" Cc: Dave Chinner , Eric Sandeen , linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-btrfs , linux-fsdevel , ocfs2-devel@oss.oracle.com Content-Type: text/plain; charset="UTF-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Oct 11, 2018 at 5:13 AM Darrick J. Wong w= rote: > > From: Darrick J. Wong > > A deduplication data corruption is exposed by fstests generic/505 on > XFS. (and btrfs) Btw, the generic test I wrote was indeed numbered 505, however it was never committed and there's now a generic/505 which has nothing to do with deduplication. So you should update the changelog to avoid confusion. thanks > It is caused by extending the block match range to include the > partial EOF block, but then allowing unknown data beyond EOF to be > considered a "match" to data in the destination file because the > comparison is only made to the end of the source file. This corrupts the > destination file when the source extent is shared with it. > > The VFS remapping prep functions only support whole block dedupe, but > we still need to appear to support whole file dedupe correctly. Hence > if the dedupe request includes the last block of the souce file, don't > include it in the actual dedupe operation. If the rest of the range > dedupes successfully, then reject the entire request. A subsequent > patch will enable us to shorten dedupe requests correctly. > > When reflinking sub-file ranges, a data corruption can occur when the > source file range includes a partial EOF block. This shares the unknown > data beyond EOF into the second file at a position inside EOF, exposing > stale data in the second file. > > If the reflink request includes the last block of the souce file, only > proceed with the reflink operation if it lands at or past the > destination file's current EOF. If it lands within the destination file > EOF, reject the entire request with -EINVAL and make the caller go the > hard way. A subsequent patch will enable us to shorten reflink requests > correctly. > > Signed-off-by: Darrick J. Wong > --- > fs/read_write.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > > diff --git a/fs/read_write.c b/fs/read_write.c > index d6e8e242a15f..8498991e2f33 100644 > --- a/fs/read_write.c > +++ b/fs/read_write.c > @@ -1723,6 +1723,7 @@ int vfs_clone_file_prep(struct file *file_in, loff_= t pos_in, > { > struct inode *inode_in =3D file_inode(file_in); > struct inode *inode_out =3D file_inode(file_out); > + u64 blkmask =3D i_blocksize(inode_in) - 1; > bool same_inode =3D (inode_in =3D=3D inode_out); > int ret; > > @@ -1785,6 +1786,27 @@ int vfs_clone_file_prep(struct file *file_in, loff= _t pos_in, > return -EBADE; > } > > + /* Are we doing a partial EOF block remapping of some kind? */ > + if (*len & blkmask) { > + /* > + * If the dedupe data matches, don't try to dedupe the pa= rtial > + * EOF block. > + * > + * If the user is attempting to remap a partial EOF block= and > + * it's inside the destination EOF then reject it. > + * > + * We don't support shortening requests, so we can only r= eject > + * them. > + */ > + if (is_dedupe) > + ret =3D -EBADE; > + else if (pos_out + *len < i_size_read(inode_out)) > + ret =3D -EINVAL; > + > + if (ret) > + return ret; > + } > + > return 1; > } > EXPORT_SYMBOL(vfs_clone_file_prep); > --=20 Filipe David Manana, =E2=80=9CWhether you think you can, or you think you can't =E2=80=94 you're= right.=E2=80=9D