linux-kernel - Re: [PATCH] rpcrdma_decode_msg: check xdr_inline

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Message-Id: <AE745E5F-63A8-4377-98E8-512828179FC0@oracle.com>
Date:   Tue, 23 Jul 2019 22:02:09 -0400
From:   Chuck Lever <chuck.lever@...cle.com>
To:     Navid Emamdoost <navid.emamdoost@...il.com>
Cc:     emamd001@....edu, kjlu@....edu, smccaman@....edu,
        secalert@...hat.com,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        "David S. Miller" <davem@...emloft.net>, linux-nfs@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rpcrdma_decode_msg: check xdr_inline_decode result



> On Jul 23, 2019, at 9:51 PM, Navid Emamdoost <navid.emamdoost@...il.com> wrote:
> 
> xdr_inline_decode may return NULL, so the check is necessary. The base
> pointer will be dereferenced later in rpcrdma_inline_fixup.

NACK. When xdr_inline_decode is passed a zero “length” argument, it can never return NULL.


> Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>
> ---
> net/sunrpc/xprtrdma/rpc_rdma.c | 3 +++
> 1 file changed, 3 insertions(+)
> 
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index 4345e6912392..d0479efe0e72 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -1160,6 +1160,9 @@ rpcrdma_decode_msg(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep,
> 
>    /* Build the RPC reply's Payload stream in rqst->rq_rcv_buf */
>    base = (char *)xdr_inline_decode(xdr, 0);
> +    if (!base)
> +        return -EIO;
> +
>    rpclen = xdr_stream_remaining(xdr);
>    r_xprt->rx_stats.fixup_copy_count +=
>        rpcrdma_inline_fixup(rqst, base, rpclen, writelist & 3);
> -- 
> 2.17.1
>