Return-Path: Received: from fieldses.org ([173.255.197.46]:60194 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754870AbcGHUya (ORCPT ); Fri, 8 Jul 2016 16:54:30 -0400 Date: Fri, 8 Jul 2016 16:54:13 -0400 From: "J. Bruce Fields" To: Oleg Drokin Cc: Jeff Layton , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] nfsd: Make creates return EEXIST correctly instead of EPERM Message-ID: <20160708205413.GC11269@fieldses.org> References: <1467942466-3081422-1-git-send-email-green@linuxhacker.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1467942466-3081422-1-git-send-email-green@linuxhacker.ru> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Jul 07, 2016 at 09:47:46PM -0400, Oleg Drokin wrote: > It looks like we are bit overzealous about failing mkdir/create/mknod > with permission denied if the parent dir is not writeable. > Need to make sure the name does not exist first, because we need to > return EEXIST in that case. > > Signed-off-by: Oleg Drokin > --- > A very similar problem exists with symlinks, but the patch is more > involved, so assuming this one is ok, I'll send a symlink one separately. > fs/nfsd/nfs4proc.c | 6 +++++- > fs/nfsd/vfs.c | 11 ++++++++++- > 2 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > index de1ff1d..0067520 100644 > --- a/fs/nfsd/nfs4proc.c > +++ b/fs/nfsd/nfs4proc.c > @@ -605,8 +605,12 @@ nfsd4_create(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, > > fh_init(&resfh, NFS4_FHSIZE); > > + /* > + * We just check thta parent is accessible here, nfsd_* do their > + * own access permission checks > + */ > status = fh_verify(rqstp, &cstate->current_fh, S_IFDIR, > - NFSD_MAY_CREATE); > + NFSD_MAY_EXEC); > if (status) > return status; > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 6fbd81e..6a45ec6 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -1161,7 +1161,11 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp, > if (isdotent(fname, flen)) > goto out; > > - err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE); > + /* > + * Even though it is a create, first we see if we are even allowed > + * to peek inside the parent > + */ > + err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC); Looks like in the v3 case we haven't actually locked the directory yet at this point so this check is a little race-prone. I wonder why the code's structured that way--it's confusing. --b. > if (err) > goto out; > > @@ -1211,6 +1215,11 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp, > goto out; > } > > + /* Now let's see if we actually have permissions to create */ > + err = nfsd_permission(rqstp, fhp->fh_export, dentry, NFSD_MAY_CREATE); > + if (err) > + goto out; > + > if (!(iap->ia_valid & ATTR_MODE)) > iap->ia_mode = 0; > iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type; > -- > 2.7.4