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 <[email protected]> > --- > 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
