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Fri, 13 Nov 2026 17:25:11 +0000 From: Bjoern Doebel To: Sasha Levin CC: Bjoern Doebel , , Chuck Lever Subject: Re: [PATCH 5.10.y v2] SUNRPC: Copy the deferred RPC Call from the head buffer Date: Fri, 13 Nov 2026 17:24:53 +0000 Message-ID: <20261113172457.222949-1-doebel@amazon.de> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: EX19D031UWC004.ant.amazon.com (10.13.139.246) To EX19D001UWA001.ant.amazon.com (10.13.138.214) Hi Sasha,=0D =0D thanks for raising this. I sent a v3 earlier in this thread ([PATCH=0D 5.10.y v3]) that reworks the backport instead of applying the upstream=0D mechanics.=0D =0D The short version: on 5.10, header parsing advances rq_arg.head[0]=0D via svc_getnl() without updating xdr_buf::len, so=0D rq_arg.len > head[0].iov_len for every Call at svc_defer() time. The=0D upstream guard would refuse every deferral, and copying from=0D head[0].iov_base would drop the headers svc_deferred_recv() expects.=0D v3 therefore keeps the skip-based snapshot and refuses deferral only=0D once a GSS integrity/privacy unwrap has run (rq_auth_slack !=3D 0) or=0D when len < head[0].iov_len, since gss_unwrap_kerberos_v2() resets=0D buf->len.=0D =0D The same rework applies to 5.15 and 6.1. The assumption upstream relies=0D on only holds since header parsing moved to xdr_stream in v6.3=0D (163cdfca341b7, "SUNRPC: Decode most of RPC header with xdr_stream");=0D 5.15 and 6.1 still use svc_getnl(). I see the verbatim patch is=0D already queued for both trees - it will refuse all deferrals there,=0D just like my v2 would have on 5.10.=0D =0D Want me to send v3-style backports for 5.15.y and 6.1.y?=0D =0D Best regards,=0D Bjoern=0D