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Bruce Fields" , Chuck Lever Cc: linux-nfs@vger.kernel.org, Volodymyr Khomenko References: <20211001135921.GC959@fieldses.org> From: Daniel Kobras Organization: Puzzle ITC Deutschland GmbH Subject: Re: [PATCH] SUNRPC: fix sign error causing rpcsec_gss drops Message-ID: <31738001-8f5b-61c9-67b6-810e6f188318@puzzle-itc.de> Date: Fri, 1 Oct 2021 18:50:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20211001135921.GC959@fieldses.org> Content-Type: text/plain; charset="UTF-8" Content-Language: en-US Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org Hi Bruce! Am 01.10.21 um 15:59 schrieb J. Bruce Fields: > From: "J. Bruce Fields" >=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") I wonder about the Fixes tag: That changeset added tracepoints to the exit path, but the buggy logic seems to have been present since the pre-git ages. Or am I missing something about 10b9d99a3dbb? (This might explain some reports of--as you stated elsewhere--"once in a blue moon my krb5 mounts hang" we've investigated, albeit on kernels that predate 10b9d99a3dbb.) Kind regards, Daniel > Cc: stable@vger.kernel.org > Signed-off-by: J. Bruce Fields > --- > 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 --=20 Daniel Kobras Principal Architect Puzzle ITC Deutschland +49 7071 14316 0 www.puzzle-itc.de --=20 Puzzle ITC Deutschland GmbH Sitz der Gesellschaft: Eisenbahnstra=C3=9Fe 1, 72072=20 T=C3=BCbingen Eingetragen am Amtsgericht Stuttgart HRB 765802 Gesch=C3=A4ftsf=C3=BChrer:=20 Lukas Kallies, Daniel Kobras, Mark Pr=C3=B6hl