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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20190315121813.GY2217@ZenIV.linux.org.uk>
References: <20190315121813.GY2217@ZenIV.linux.org.uk> <20190315074307.GA31430@light.dominikbrodowski.net> <3476.1552650285@warthog.procyon.org.uk> <20190315115002.GA9055@light.dominikbrodowski.net>
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     dhowells@redhat.com,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>, cgroups@vger.kernel.org,
        fenghua.yu@intel.com, linux-kernel@vger.kernel.org
Subject: Re: fs_context-related oops in mainline
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Date:   Fri, 15 Mar 2019 14:24:30 +0000
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Al Viro <viro@zeniv.linux.org.uk> wrote:

> -	if (fc->user_ns)
> -		put_user_ns(fc->user_ns);
> -	fc->user_ns = get_user_ns(netns->user_ns);
> +	if (netns) {
> +		if (fc->user_ns)
> +			put_user_ns(fc->user_ns);
> +		fc->user_ns = get_user_ns(netns->user_ns);
> +	}

This begs the question why is sysfs using the current network namespace's idea
of the user namespace?  Why not just use the one directly from current->cred?

David