linux-kernel - Re: fs_context-related oops in mainline

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Message-ID: <20190315114632.GA8896@light.dominikbrodowski.net>
Date:   Fri, 15 Mar 2019 12:46:32 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     David Howells <dhowells@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        fenghua.yu@...el.com, linux-kernel@...r.kernel.org
Subject: Re: fs_context-related oops in mainline

On Fri, Mar 15, 2019 at 11:34:47AM +0000, Al Viro wrote:
> On Fri, Mar 15, 2019 at 08:43:07AM +0100, Dominik Brodowski wrote:
> > David, Al,
> > 
> > commit 23bf1b6be9c2 ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context")
> > seems to have introduced a bug; at least that's the commit I bisected the
> > following oops down to:

As additional information: In sysfs_init_fs_context, we have

	kfc->ns_tag = netns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
	...
	fc->user_ns = get_user_ns(netns->user_ns);

With my config, kobj_ns_grab_current() returns NULL here, which obviously
causes a null pointer dereference when trying to set fs->user_ns.

Probably the most important line of the .config (attached):

	# CONFIG_NET is not set

Thanks,
	Dominik

View attachment "config" of type "text/plain" (46463 bytes)