linux-kernel - Re: [PATCH 5.10 045/146] net: make get_net_ns return error if NET

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Message-ID: <20210627085759.n75m3uulvll47bdf@mail.google.com>
Date:   Sun, 27 Jun 2021 16:57:59 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Changbin Du <changbin.du@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Laight <David.Laight@...LAB.COM>,
        Christian Brauner <christian.brauner@...ntu.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 045/146] net: make get_net_ns return error if NET_NS
 is disabled

On Wed, Jun 23, 2021 at 04:26:35PM +0200, Pavel Machek wrote:
> Hi!
> > 
> > There is a panic in socket ioctl cmd SIOCGSKNS when NET_NS is not enabled.
> > The reason is that nsfs tries to access ns->ops but the proc_ns_operations
> > is not implemented in this case.
> > 
> > [7.670023] Unable to handle kernel NULL pointer dereference at virtual address 00000010
> > [7.670268] pgd = 32b54000
> > [7.670544] [00000010] *pgd=00000000
> > [7.671861] Internal error: Oops: 5 [#1] SMP ARM
> > [7.672315] Modules linked in:
> > [7.672918] CPU: 0 PID: 1 Comm: systemd Not tainted 5.13.0-rc3-00375-g6799d4f2da49 #16
> > [7.673309] Hardware name: Generic DT based system
> > [7.673642] PC is at nsfs_evict+0x24/0x30
> > [7.674486] LR is at clear_inode+0x20/0x9c
> > 
> > The same to tun SIOCGSKNS command.
> > 
> > To fix this problem, we make get_net_ns() return -EINVAL when NET_NS is
> > disabled. Meanwhile move it to right place net/core/net_namespace.c.
> 
> -EINVAL sounds like wrong error code for valid operation kernel was
> configured to do. -ENOTSUPP?
>
This is to align with the existing code which returns -EINVAL.
For the issue we fixed, yes, -EOPNOTSUPP (not -ENOTSUPP) should be better.

> Best regards,
> 								Pavel
> 								
> -- 
> http://www.livejournal.com/~pavelmachek



-- 
Cheers,
Changbin Du