netdev - Re: [PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup

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Message-ID: <ce2ef435-7c59-01f1-c1bf-4405f44fd0f9@iogearbox.net>
Date: Tue, 9 Jul 2024 00:21:08 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: kuba@...nel.org
Cc: netdev@...r.kernel.org, linux-nfs@...r.kernel.org,
 Lex Siegel <usiegl00@...il.com>, Neil Brown <neilb@...e.de>,
 Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>
Subject: Re: [PATCH net v3 resend] net, sunrpc: Remap EPERM in case of
 connection failure in xs_tcp_setup_socket

On 7/4/24 8:41 AM, Daniel Borkmann wrote:
> When using a BPF program on kernel_connect(), the call can return -EPERM. This
> causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing
> the kernel to potentially freeze up.
> 
> Neil suggested:
> 
>    This will propagate -EPERM up into other layers which might not be ready
>    to handle it. It might be safer to map EPERM to an error we would be more
>    likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.
> 
> ECONNREFUSED as error seems reasonable. For programs setting a different error
> can be out of reach (see handling in 4fbac77d2d09) in particular on kernels
> which do not have f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err
> instead of allow boolean"), thus given that it is better to simply remap for
> consistent behavior. UDP does handle EPERM in xs_udp_send_request().
> 
> Fixes: d74bad4e74ee ("bpf: Hooks for sys_connect")
> Fixes: 4fbac77d2d09 ("bpf: Hooks for sys_bind")
> Co-developed-by: Lex Siegel <usiegl00@...il.com>
> Signed-off-by: Lex Siegel <usiegl00@...il.com>
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Cc: Neil Brown <neilb@...e.de>
> Cc: Trond Myklebust <trondmy@...nel.org>
> Cc: Anna Schumaker <anna@...nel.org>
> Link: https://github.com/cilium/cilium/issues/33395
> Link: https://lore.kernel.org/bpf/171374175513.12877.8993642908082014881@noble.neil.brown.name
> ---
>   [ Fixes tags are set to the orig connect commit so that stable team
>     can pick this up.
> 
>     Resend as it turns out that patchwork did not pick up the earlier
>     resends likely due to the message id being the same. ]
> 
>   v1 -> v2 -> v3:
>     - Plain resend, adding correct sunrpc folks to Cc
>       https://lore.kernel.org/bpf/Zn7wtStV+iafWRXj@tissot.1015granger.net/

(gentle ping)