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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Bruce Fields <bfields@fieldses.org>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Volodymyr Khomenko <volodymyr@vastdata.com>
Subject: Re: [PATCH] SUNRPC: fix sign error causing rpcsec_gss drops
Thread-Topic: [PATCH] SUNRPC: fix sign error causing rpcsec_gss drops
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Date:   Fri, 1 Oct 2021 16:00:55 +0000
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References: <20211001135921.GC959@fieldses.org>
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> On Oct 1, 2021, at 9:59 AM, J. Bruce Fields <bfields@fieldses.org> wrote:
>=20
> From: "J. Bruce Fields" <bfields@redhat.com>
>=20
> If sd_max is unsigned, then sd_max - GSS_SEQ_WIN is a very large number
> whenever sd_max is less than GSS_SEQ_WIN, and the comparison:
>=20
> 	seq_num <=3D sd->sd_max - GSS_SEQ_WIN
>=20
> in gss_check_seq_num is pretty much always true, even when that's
> clearly not what was intended.
>=20
> This was causing pynfs to hang when using krb5, because pynfs uses zero
> as the initial gss sequence number.  That's perfectly legal, but this
> logic error causes knfsd to drop the rpc in that case.  Out-of-order
> sequence IDs in the first GSS_SEQ_WIN (128) calls will also cause this.
>=20
> Fixes: 10b9d99a3dbb ("SUNRPC: Augment server-side rpcgss tracepoints")
> Cc: stable@vger.kernel.org
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>

This will be included in the next NFSD 5.15-rc. Thanks!
See the for-next branch at

git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git


> ---
> net/sunrpc/auth_gss/svcauth_gss.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svca=
uth_gss.c
> index 7dba6a9c213a..b87565b64928 100644
> --- a/net/sunrpc/auth_gss/svcauth_gss.c
> +++ b/net/sunrpc/auth_gss/svcauth_gss.c
> @@ -645,7 +645,7 @@ static bool gss_check_seq_num(const struct svc_rqst *=
rqstp, struct rsc *rsci,
> 		}
> 		__set_bit(seq_num % GSS_SEQ_WIN, sd->sd_win);
> 		goto ok;
> -	} else if (seq_num <=3D sd->sd_max - GSS_SEQ_WIN) {
> +	} else if (seq_num + GSS_SEQ_WIN <=3D sd->sd_max) {
> 		goto toolow;
> 	}
> 	if (__test_and_set_bit(seq_num % GSS_SEQ_WIN, sd->sd_win))
> --=20
> 2.31.1
>=20

--
Chuck Lever