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Date: Wed, 18 Oct 2023 08:13:41 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Jiri Pirko <jiri@resnulli.us>
Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com,
 pabeni@redhat.com, przemyslaw.kitszel@intel.com, daniel@iogearbox.net,
 opurdila@ixiacom.com
Subject: Re: [PATCH net v2 1/5] net: fix ifname in netlink ntf during netns
 move
Message-ID: <20231018081341.66bf393b@kernel.org>
In-Reply-To: <ZS+FehME4fC4b7w4@nanopsycho>
References: <20231018013817.2391509-1-kuba@kernel.org>
	<20231018013817.2391509-2-kuba@kernel.org>
	<ZS+FehME4fC4b7w4@nanopsycho>
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On Wed, 18 Oct 2023 09:12:58 +0200 Jiri Pirko wrote:
> >+static int dev_prep_valid_name(struct net *net, struct net_device *dev,
> >+			       const char *want_name, char *out_name)
> >+{
> >+	int ret;
> >+
> >+	if (!dev_valid_name(want_name))
> >+		return -EINVAL;
> >+
> >+	if (strchr(want_name, '%')) {
> >+		ret = __dev_alloc_name(net, want_name, out_name);
> >+		return ret < 0 ? ret : 0;
> >+	} else if (netdev_name_in_use(net, want_name)) {
> >+		return -EEXIST;
> >+	} else if (out_name != want_name) {  
> 
> How this can happen?
> You call dev_prep_valid_name() twice:
> 	ret = dev_prep_valid_name(net, dev, name, buf);
> 	err = dev_prep_valid_name(net, dev, pat, new_name);
> 
> Both buf and new_name are on stack tmp variables.

I'm moving this code 1-to-1. I have patches queued up to clean all 
this up in net-next. Please let me know if you see any bugs.