Re: [PATCH v14 04/25] NFSD: Handle @rqstp == NULL in check_nfsd_access()

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2024-08-28 at 21:03 -0400, Mike Snitzer wrote:
> From: NeilBrown <neilb@suse.de>
> 
> LOCALIO-initiated open operations are not running in an nfsd thread
> and thus do not have an associated svc_rqst context.
> 
> Signed-off-by: NeilBrown <neilb@suse.de>
> Co-developed-by: Mike Snitzer <snitzer@kernel.org>
> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfsd/export.c | 30 +++++++++++++++++++++++++-----
>  1 file changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> index 7bb4f2075ac5..c82d8e3e0d4f 100644
> --- a/fs/nfsd/export.c
> +++ b/fs/nfsd/export.c
> @@ -1074,10 +1074,30 @@ static struct svc_export *exp_find(struct cache_detail *cd,
>  	return exp;
>  }
>  
> +/**
> + * check_nfsd_access - check if access to export is allowed.
> + * @exp: svc_export that is being accessed.
> + * @rqstp: svc_rqst attempting to access @exp (will be NULL for LOCALIO).
> + *
> + * Return values:
> + *   %nfs_ok if access is granted, or
> + *   %nfserr_wrongsec if access is denied
> + */
>  __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
>  {
>  	struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;
> -	struct svc_xprt *xprt = rqstp->rq_xprt;
> +	struct svc_xprt *xprt;
> +
> +	/*
> +	 * If rqstp is NULL, this is a LOCALIO request which will only
> +	 * ever use a filehandle/credential pair for which access has
> +	 * been affirmed (by ACCESS or OPEN NFS requests) over the
> +	 * wire. So there is no need for further checks here.
> +	 */
> +	if (!rqstp)
> +		return nfs_ok;
> +
> +	xprt = rqstp->rq_xprt;
>  
>  	if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_NONE) {
>  		if (!test_bit(XPT_TLS_SESSION, &xprt->xpt_flags))
> @@ -1098,17 +1118,17 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
>  ok:
>  	/* legacy gss-only clients are always OK: */
>  	if (exp->ex_client == rqstp->rq_gssclient)
> -		return 0;
> +		return nfs_ok;
>  	/* ip-address based client; check sec= export option: */
>  	for (f = exp->ex_flavors; f < end; f++) {
>  		if (f->pseudoflavor == rqstp->rq_cred.cr_flavor)
> -			return 0;
> +			return nfs_ok;
>  	}
>  	/* defaults in absence of sec= options: */
>  	if (exp->ex_nflavors == 0) {
>  		if (rqstp->rq_cred.cr_flavor == RPC_AUTH_NULL ||
>  		    rqstp->rq_cred.cr_flavor == RPC_AUTH_UNIX)
> -			return 0;
> +			return nfs_ok;
>  	}
>  
>  	/* If the compound op contains a spo_must_allowed op,
> @@ -1118,7 +1138,7 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
>  	 */
>  
>  	if (nfsd4_spo_must_allow(rqstp))
> -		return 0;
> +		return nfs_ok;
>  
>  denied:
>  	return nfserr_wrongsec;

Reviewed-by: Jeff Layton <jlayton@kernel.org>