Re: [PATCH 1/5] SUNRPC: Reject add_xprt on a backchannel xprt_switch

[sashiko-bot@kernel.org]

> The add_xprt sysfs file clones the main transport of an xprt_switch,
> including its bc_xprt. On the xprt_switch of an NFSv4.1 callback
> client, the clone runs a backchannel setup routine against the main
> transport's svc_xprt. xs_setup_bc_tcp() overwrites xpt_bc_xprt
> without releasing the reference the original rpc_xprt held there, so
> the original rpc_xprt leaks along with its netns and module
> references. On an RDMA callback client the same write oopses
> instead, because the RDMA backchannel transport leaves xprt_class
> NULL.
> 
> A backchannel transport rides on its svc_xprt and has no connection
> of its own to clone. Return -EOPNOTSUPP when the main transport has
> a bc_xprt, before reading its xprt_class, as
> rpc_sysfs_xprt_dstaddr_store() does for transports other than TCP
> and RDMA.
> 
> Fixes: df210d9b0951 ("sunrpc: Add a sysfs file for adding a new xprt")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chuck Lever <cel@kernel.org>

Sashiko has reviewed this patch and found no issues.

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