linux-kernel - Re: [PATCH v2 1/2] sunrpc: account for TCP record marker in rq

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Message-id: <175995916318.1793333.16943216276808147348@noble.neil.brown.name>
Date: Thu, 09 Oct 2025 08:32:43 +1100
From: NeilBrown <neilb@...mail.net>
To: "Jeff Layton" <jlayton@...nel.org>
Cc: "Chuck Lever" <chuck.lever@...cle.com>,
 "Olga Kornievskaia" <okorniev@...hat.com>, "Dai Ngo" <Dai.Ngo@...cle.com>,
 "Tom Talpey" <tom@...pey.com>, "Trond Myklebust" <trondmy@...nel.org>,
 "Anna Schumaker" <anna@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 "Eric Dumazet" <edumazet@...gle.com>, "Jakub Kicinski" <kuba@...nel.org>,
 "Paolo Abeni" <pabeni@...hat.com>, "Simon Horman" <horms@...nel.org>,
 "David Howells" <dhowells@...hat.com>, "Brandon Adams" <brandona@...a.com>,
 linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, "Jeff Layton" <jlayton@...nel.org>
Subject: Re: [PATCH v2 1/2] sunrpc: account for TCP record marker in rq_bvec
 array when sending

On Thu, 09 Oct 2025, Jeff Layton wrote:
> The call to xdr_buf_to_bvec() in svc_tcp_sendto() passes in the second
> slot to the bvec array as the starting slot, but doesn't decrease the
> length of the array by one.
> 
> Fixes: 59cf7346542b ("sunrpc: Replace the rq_bvec array with dynamically-allocated memory")
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
>  net/sunrpc/svcsock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 7b90abc5cf0ee1520796b2f38fcb977417009830..377fcaaaa061463fc5c85fc09c7a8eab5e06af77 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1244,7 +1244,7 @@ static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp,
>  	memcpy(buf, &marker, sizeof(marker));
>  	bvec_set_virt(rqstp->rq_bvec, buf, sizeof(marker));
>  
> -	count = xdr_buf_to_bvec(rqstp->rq_bvec + 1, rqstp->rq_maxpages,
> +	count = xdr_buf_to_bvec(rqstp->rq_bvec + 1, rqstp->rq_maxpages - 1,
>  				&rqstp->rq_res);

oh - that's embarrassing :-(

Reviewed-by: NeilBrown <neil@...wn.name>

Thanks,
NeilBrown

>  
>  	iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
> 
> -- 
> 2.51.0
> 
>