[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <2cf128ed-cd74-4025-8ae8-28934abbf25a@redhat.com>
Date: Thu, 15 Aug 2024 18:07:20 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Breno Leitao <leitao@...ian.org>
Cc: kuba@...nel.org, davem@...emloft.net, edumazet@...gle.com,
thepacketgeek@...il.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Aijay Adams <aijay@...a.com>
Subject: Re: [PATCH net-next] net: netconsole: Populate dynamic entry even if
netpoll fails
On 8/15/24 15:46, Breno Leitao wrote:
> On Wed, Aug 14, 2024 at 12:06:48PM +0200, Paolo Abeni wrote:
>> I fear the late cleanup could still be dangerous - what if multiple,
>> consecutive, enabled_store() on the same target fails?
>>
>> I *think* it would be safer always zeroing np->dev in the error path of
>> netpoll_setup().
>>
>> It could be a separate patch for bisectability.
>>
>> Side note: I additionally think that in the same error path we should
>> conditionally clear np->local_ip.ip, if the previous code initialized such
>> field, or we could get weird results if e.g.
>> - a target uses eth0 with local_ip == 0
>> - enabled_store() of such target fails e.g. due ndo_netpoll_setup() failure
>> - address on eth0 changes for some reason
>> - anoter enabled_store() is issued on the same target.
>>
>> At this point the netpoll target should be wrongly using the old address.
>
> Agree with you. I think we always want to keep struct netpoll objects
> either initialized or unitialized, not keeping them half-baked.
>
> How about the following patch:
Overall LGTM, a couple of minor comments below.
> netpoll: Ensure clean state on setup failures
>
> Modify netpoll_setup() and __netpoll_setup() to ensure that the netpoll
> structure (np) is left in a clean state if setup fails for any reason.
> This prevents carrying over misconfigured fields in case of partial
> setup success.
>
> Key changes:
> - np->dev is now set only after successful setup, ensuring it's always
> NULL if netpoll is not configured or if netpoll_setup() fails.
> - np->local_ip is zeroed if netpoll setup doesn't complete successfully.
> - Added DEBUG_NET_WARN_ON_ONCE() checks to catch unexpected states.
>
> These changes improve the reliability of netpoll configuration, since it
> assures that the structure is fully initialized or totally unset.
>
> Suggested-by: Paolo Abeni <pabeni@...hat.com>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
>
> diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> index a58ea724790c..348d76a51c20 100644
> --- a/net/core/netpoll.c
> +++ b/net/core/netpoll.c
> @@ -626,12 +626,10 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
> const struct net_device_ops *ops;
> int err;
>
> - np->dev = ndev;
> - strscpy(np->dev_name, ndev->name, IFNAMSIZ);
> -
> + DEBUG_NET_WARN_ON_ONCE(np->dev);
> if (ndev->priv_flags & IFF_DISABLE_NETPOLL) {
> np_err(np, "%s doesn't support polling, aborting\n",
> - np->dev_name);
> + ndev->name);
> err = -ENOTSUPP;
> goto out;
> }
> @@ -649,7 +647,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
>
> refcount_set(&npinfo->refcnt, 1);
>
> - ops = np->dev->netdev_ops;
> + ops = ndev->netdev_ops;
> if (ops->ndo_netpoll_setup) {
> err = ops->ndo_netpoll_setup(ndev, npinfo);
> if (err)
> @@ -660,6 +658,8 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
> refcount_inc(&npinfo->refcnt);
> }
>
> + np->dev = ndev;
> + strscpy(np->dev_name, ndev->name, IFNAMSIZ);
> npinfo->netpoll = np;
>
> /* last thing to do is link it to the net device structure */
> @@ -681,6 +681,7 @@ int netpoll_setup(struct netpoll *np)
> int err;
>
> rtnl_lock();
> + DEBUG_NET_WARN_ON_ONCE(np->dev);
This looks redundant
> if (np->dev_name[0]) {
> struct net *net = current->nsproxy->net_ns;
> ndev = __dev_get_by_name(net, np->dev_name);
> @@ -782,11 +783,14 @@ int netpoll_setup(struct netpoll *np)
>
> err = __netpoll_setup(np, ndev);
> if (err)
> - goto put;
> + goto clear_ip;
> rtnl_unlock();
> return 0;
>
> +clear_ip:
> + memset(&np->local_ip, 0, sizeof(np->local_ip));
I think it would be better to clear the local_ip only if np->local_ip
was set/initialized/filled by netpoll_setup() otherwise the sysfs
contents could suddenly/unexpetedly change on failure.
Thanks,
Paolo
Powered by blists - more mailing lists