NFSv4: Check for buffer length in __nfs4_get_acl_uncached

Commit 1f1ea6c "NFSv4: Fix buffer overflow checking in
__nfs4_get_acl_uncached" accidently dropped the checking for too small
result buffer length.

If someone uses getxattr on "system.nfs4_acl" on an NFSv4 mount
supporting ACLs, the ACL has not been cached and the buffer suplied is
too short, we still copy the complete ACL, resulting in kernel and user
space memory corruption.

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
Cc: stable@kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
static int nfs4_proc_lookup(struct inode *dir, struct qstr *name,
			    struct nfs_fh *fhandle, struct nfs_fattr *fattr)
{
	int status;
	struct rpc_clnt *client = NFS_CLIENT(dir);

	status = nfs4_proc_lookup_common(&client, dir, name, fhandle, fattr);
	if (client != NFS_CLIENT(dir)) {
		rpc_shutdown_client(client);
		nfs_fixup_secinfo_attributes(fattr);
	}
	return status;
}

static int nfs4_proc_lookup(struct inode *dir, struct qstr *name,
			    struct nfs_fh *fhandle, struct nfs_fattr *fattr)
{
	int status;
	struct rpc_clnt *client = NFS_CLIENT(dir);

	status = nfs4_proc_lookup_common(&client, dir, name, fhandle, fattr);
	if (client != NFS_CLIENT(dir)) {
		rpc_shutdown_client(client);
		nfs_fixup_secinfo_attributes(fattr);
	}
	return status;
}
