From patchwork Thu Feb 9 16:01:31 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "J. Bruce Fields" X-Patchwork-Id: 9565051 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 961EB60572 for ; Thu, 9 Feb 2017 16:03:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8438E283E8 for ; Thu, 9 Feb 2017 16:03:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 76F4C28427; Thu, 9 Feb 2017 16:03:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D582C283E8 for ; Thu, 9 Feb 2017 16:03:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753490AbdBIQCa (ORCPT ); Thu, 9 Feb 2017 11:02:30 -0500 Received: from fieldses.org ([173.255.197.46]:46310 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750947AbdBIQC3 (ORCPT ); Thu, 9 Feb 2017 11:02:29 -0500 Received: by fieldses.org (Postfix, from userid 2815) id 5AF55242F; Thu, 9 Feb 2017 11:01:31 -0500 (EST) Date: Thu, 9 Feb 2017 11:01:31 -0500 From: "J. Bruce Fields" To: Christoph Hellwig Cc: chucklever@gmail.com, linux-nfs@vger.kernel.org Subject: Re: [PATCH] nfsd: restore owner override for truncate Message-ID: <20170209160131.GE17622@fieldses.org> References: <20170209142238.5322-1-hch@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20170209142238.5322-1-hch@lst.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Thu, Feb 09, 2017 at 03:22:38PM +0100, Christoph Hellwig wrote: > The switch to vfs_truncate in nfsd_setattr dropped the owner override > used for NFS permissions. Add a copy of vfs_truncate with it restored > to the nfsd code for now as it's very late in the cycle, but there > should be a way to consolidate it back in the future. This also needs: --b. > > Fixes: 41f53350 ("nfsd: special case truncates some more") > Signed-off-by: Christoph Hellwig > Reported-by: Chuck Lever > --- > fs/nfsd/vfs.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 80 insertions(+), 1 deletion(-) > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index a974368026a1..fd4a32e0b0b4 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -332,6 +332,85 @@ nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap) > } > } > > +/* copy of vfs_truncate with NFS owner override hacked in, sigh.. */ > +static long nfsd_truncate(const struct path *path, loff_t length) > +{ > + struct inode *inode; > + struct dentry *upperdentry; > + long error; > + > + inode = path->dentry->d_inode; > + > + /* For directories it's -EISDIR, for other non-regulars - -EINVAL */ > + if (S_ISDIR(inode->i_mode)) > + return -EISDIR; > + if (!S_ISREG(inode->i_mode)) > + return -EINVAL; > + > + error = mnt_want_write(path->mnt); > + if (error) > + goto out; > + > + /* > + * The file owner always gets access permission for accesses that > + * would normally be checked at open time. This is to make > + * file access work even when the client has done a fchmod(fd, 0). > + * > + * However, `cp foo bar' should fail nevertheless when bar is > + * readonly. A sensible way to do this might be to reject all > + * attempts to truncate a read-only file, because a creat() call > + * always implies file truncation. > + * ... but this isn't really fair. A process may reasonably call > + * ftruncate on an open file descriptor on a file with perm 000. > + * We must trust the client to do permission checking - using "ACCESS" > + * with NFSv3. > + */ > + if (!uid_eq(inode->i_uid, current_fsuid())) { > + error = inode_permission(inode, MAY_WRITE); > + if (error) > + goto mnt_drop_write_and_out; > + } > + > + error = -EPERM; > + if (IS_APPEND(inode)) > + goto mnt_drop_write_and_out; > + > + /* > + * If this is an overlayfs then do as if opening the file so we get > + * write access on the upper inode, not on the overlay inode. For > + * non-overlay filesystems d_real() is an identity function. > + */ > + upperdentry = d_real(path->dentry, NULL, O_WRONLY); > + error = PTR_ERR(upperdentry); > + if (IS_ERR(upperdentry)) > + goto mnt_drop_write_and_out; > + > + error = get_write_access(upperdentry->d_inode); > + if (error) > + goto mnt_drop_write_and_out; > + > + /* > + * Make sure that there are no leases. get_write_access() protects > + * against the truncate racing with a lease-granting setlease(). > + */ > + error = break_lease(inode, O_WRONLY); > + if (error) > + goto put_write_and_out; > + > + error = locks_verify_truncate(inode, NULL, length); > + if (!error) > + error = security_path_truncate(path); > + if (!error) > + error = do_truncate(path->dentry, length, 0, NULL); > + > +put_write_and_out: > + put_write_access(upperdentry->d_inode); > +mnt_drop_write_and_out: > + mnt_drop_write(path->mnt); > +out: > + return error; > +} > + > /* > * Set various file attributes. After this call fhp needs an fh_put. > */ > @@ -398,7 +477,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap, > ((iap->ia_valid & ~(ATTR_SIZE | ATTR_MTIME)) == 0)) > implicit_mtime = true; > > - host_err = vfs_truncate(&path, iap->ia_size); > + host_err = nfsd_truncate(&path, iap->ia_size); > if (host_err) > goto out_host_err; > > -- > 2.11.0 Tested-by: Chuck Lever --- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/open.c b/fs/open.c index 9921f70bc5ca..5d8126b230d9 100644 --- a/fs/open.c +++ b/fs/open.c @@ -64,6 +64,7 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs, inode_unlock(dentry->d_inode); return ret; } +EXPORT_SYMBOL_GPL(do_truncate); long vfs_truncate(const struct path *path, loff_t length) {