linux-kernel - Re: ls input/output error ("NFS: readdir(/) returns -5") on krb5 NFSv4 client using SHA2

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Message-ID: <e5112807-a427-4762-b7b9-ecaa95fa0482@oracle.com>
Date: Mon, 17 Nov 2025 08:41:03 -0500
From: Chuck Lever <chuck.lever@...cle.com>
To: "Tyler W. Ross" <TWR@...erwross.com>, Trond Myklebust <trondmy@...nel.org>
Cc: Anna Schumaker <anna@...nel.org>,
        Salvatore Bonaccorso
 <carnil@...ian.org>,
        "1120598@...s.debian.org" <1120598@...s.debian.org>,
        Jeff Layton <jlayton@...nel.org>, NeilBrown <neil@...wn.name>,
        Scott Mayhew <smayhew@...hat.com>, Steve Dickson <steved@...hat.com>,
        Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>,
        Tom Talpey <tom@...pey.com>, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: ls input/output error ("NFS: readdir(/) returns -5") on krb5
 NFSv4 client using SHA2

On 11/17/25 12:19 AM, Tyler W. Ross wrote:
> Weird behavior I just discovered:
> 
> Explicitly setting allowed-enctypes in the gssd section of /etc/nfs.conf
> to exclude aes256-cts-hmac-sha1-96 makes both SHA2 ciphers work as
> expected (assuming each is allowed).
> 
> If allowed-enctypes is unset (letting gssd interrogate the kernel for
> supported enctypes) or includes aes256-cts-hmac-sha1-96, then the XDR
> overflow occurs.
> 
> Non-working configurations (first is the commented-out default in nfs.conf):
> allowed-enctypes=aes256-cts-hmac-sha384-192,aes128-cts-hmac-sha256-128,camellia256-cts-cmac,camellia128-cts-cmac,aes256-cts-hmac-sha1-96,aes128-cts-hmac-sha1-96
> allowed-enctypes=aes256-cts-hmac-sha384-192,aes256-cts-hmac-sha1-96
> allowed-enctypes=aes128-cts-hmac-sha256-128,aes256-cts-hmac-sha1-96
> allowed-enctypes=aes256-cts-hmac-sha384-192,aes128-cts-hmac-sha256-128,aes256-cts-hmac-sha1-96
> 
> Working configurations (first is default sans aes256-cts-hmac-sha1-96):
> allowed-enctypes=aes256-cts-hmac-sha384-192,aes128-cts-hmac-sha256-128,camellia256-cts-cmac,camellia128-cts-cmac,aes128-cts-hmac-sha1-96
> allowed-enctypes=aes256-cts-hmac-sha384-192,aes128-cts-hmac-sha256-128
> allowed-enctypes=aes256-cts-hmac-sha384-192,aes128-cts-hmac-sha1-96
> allowed-enctypes=aes128-cts-hmac-sha256-128,aes128-cts-hmac-sha1-96
> 
> 
> Is this gssd mishandling some setup/initialization?
> Or is there a miscalculation happening somewhere further up?
Does Debian's user space Kerberos support the sha2 enctypes?


-- 
Chuck Lever