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

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Message-ID: <ji2_uZ3RNtBdATHSokoxSrIXMAi4zh2jZXEd0WownMtXo_WNIseAeeDZoBFjT54nCE1Iw0PcGgfORC5p39CP9KGqjY6T2wqeBRGonjIjfXM=@tylerwross.com>
Date: Mon, 17 Nov 2025 05:19:38 +0000
From: "Tyler W. Ross" <TWR@...erwross.com>
To: Trond Myklebust <trondmy@...nel.org>
Cc: Chuck Lever <chuck.lever@...cle.com>, 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

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?

TWR