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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH v3 01/26] SUNRPC: Move fault injection call sites
Thread-Topic: [PATCH v3 01/26] SUNRPC: Move fault injection call sites
Thread-Index: AQHXNUYTRv+lxzAbMU2EsDrdsMoAz6q8IquA
Date:   Mon, 19 Apr 2021 18:05:42 +0000
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> On Apr 19, 2021, at 2:01 PM, Chuck Lever <chuck.lever@oracle.com> wrote:
>=20
> I've hit some crashes that occur in the xprt_rdma_inject_disconnect
> path. It appears that, for some provides, rdma_disconnect() can

^provides^providers

> take so long that the transport can disconnect and release its
> hardware resources while rdma_disconnect() is still running,
> resulting in a UAF in the provider.
>=20
> The transport's fault injection method may depend on the stability
> of transport data structures. That means it needs to be invoked
> only from contexts that hold the transport write lock.
>=20
> Fixes: 4a0682583988 ("SUNRPC: Transport fault injection")
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> net/sunrpc/clnt.c               |    1 -
> net/sunrpc/xprt.c               |    6 ++++--
> net/sunrpc/xprtrdma/transport.c |    6 ++++--
> 3 files changed, 8 insertions(+), 5 deletions(-)
>=20
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index 612f0a641f4c..c2a01125be1a 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -1799,7 +1799,6 @@ call_allocate(struct rpc_task *task)
>=20
> 	status =3D xprt->ops->buf_alloc(task);
> 	trace_rpc_buf_alloc(task, status);
> -	xprt_inject_disconnect(xprt);
> 	if (status =3D=3D 0)
> 		return;
> 	if (status !=3D -ENOMEM) {
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index 691ccf8049a4..d616b93751d8 100644
> --- a/net/sunrpc/xprt.c
> +++ b/net/sunrpc/xprt.c
> @@ -1483,7 +1483,10 @@ bool xprt_prepare_transmit(struct rpc_task *task)
>=20
> void xprt_end_transmit(struct rpc_task *task)
> {
> -	xprt_release_write(task->tk_rqstp->rq_xprt, task);
> +	struct rpc_xprt	*xprt =3D task->tk_rqstp->rq_xprt;
> +
> +	xprt_inject_disconnect(xprt);
> +	xprt_release_write(xprt, task);
> }
>=20
> /**
> @@ -1885,7 +1888,6 @@ void xprt_release(struct rpc_task *task)
> 	spin_unlock(&xprt->transport_lock);
> 	if (req->rq_buffer)
> 		xprt->ops->buf_free(task);
> -	xprt_inject_disconnect(xprt);
> 	xdr_free_bvec(&req->rq_rcv_buf);
> 	xdr_free_bvec(&req->rq_snd_buf);
> 	if (req->rq_cred !=3D NULL)
> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transp=
ort.c
> index 78d29d1bcc20..09953597d055 100644
> --- a/net/sunrpc/xprtrdma/transport.c
> +++ b/net/sunrpc/xprtrdma/transport.c
> @@ -262,8 +262,10 @@ xprt_rdma_connect_worker(struct work_struct *work)
>  * xprt_rdma_inject_disconnect - inject a connection fault
>  * @xprt: transport context
>  *
> - * If @xprt is connected, disconnect it to simulate spurious connection
> - * loss.
> + * If @xprt is connected, disconnect it to simulate spurious
> + * connection loss. Caller must hold @xprt's send lock to
> + * ensure that data structures and hardware resources are
> + * stable during the rdma_disconnect() call.
>  */
> static void
> xprt_rdma_inject_disconnect(struct rpc_xprt *xprt)
>=20
>=20

--
Chuck Lever