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Date: Mon, 14 Sep 2015 15:59:20 -0600
From: Jonathan Corbet <corbet@lwn.net>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com,
        johannes@sipsolutions.net,
        Arnaldo Carvalho de Melo <acme@infradead.org>
Subject: Re: [PATCH RFC v3 1/6] exterr: Introduce extended syscall error
 reporting
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	<1441987205-4021-2-git-send-email-alexander.shishkin@linux.intel.com>
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One more little thing:

> +int ext_err_copy_to_user(void __user *buf, size_t size)
> +{

[...]

> +        ret = copy_to_user(buf, output, len + 1);
> +
> +        kfree(output);
> +
> +	if (!ret)
> +		current->ext_err_code = 0;
> +
> +	return ret ? ret : len + 1;
> +}

I'm pretty sure you really want something like:

	return ret ? -EFAULT : (len + 1);

here.

jon