Re: [PATCH 09/10] nfsd: cap decoded POSIX ACL count to bound sort cost

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2026-05-29 at 14:34 -0400, Chuck Lever wrote:
> [ replaced broken email address for Trond ]
> 
> On Thu, May 28, 2026, at 5:55 PM, Jeff Layton wrote:
> 
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index c6c50c376b23..5469c6c207ba 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -448,6 +448,8 @@ nfsd4_decode_posixacl(struct nfsd4_compoundargs 
> > *argp, struct posix_acl **acl)
> > 
> >  	if (xdr_stream_decode_u32(argp->xdr, &count) < 0)
> >  		return nfserr_bad_xdr;
> > +	if (count > NFS_ACL_MAX_ENTRIES)
> > +		return nfserr_resource;
> 
> nfserr_resource is consistent with other fattr4 decoders, but
> does not make sense here, IMO. A better choice is nfserr_inval.
> 

Why not? An ACL that long doesn't violate the spec (as you pointed
out), the implementation just can't handle it. I do agree that
nfserr_resource is not the ideal error code, but it's the closest error
I can see that says "you hit an internal limitation of the server".

> Rick, any opinion?
> 
> 
> >  	*acl = posix_acl_alloc(count, GFP_KERNEL);
> >  	if (*acl == NULL)
> > 
> > -- 
> > 2.54.0

-- 
Jeff Layton <jlayton@kernel.org>