netdev - Re: [PATCH v3] net: make get_net_ns return error if NET

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Message-ID: <20210610105112.787a0d5f@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 10 Jun 2021 10:51:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Cong Wang <xiyou.wangcong@...il.com>,
        David Laight <David.Laight@...LAB.COM>,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: Re: [PATCH v3] net: make get_net_ns return error if NET_NS is
 disabled

On Thu, 10 Jun 2021 23:39:41 +0800 Changbin Du wrote:
> 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.

I'm assuming you went from EOPNOTSUPP to EINVAL to follow what the
existing helpers in the header do?

Acked-by: Jakub Kicinski <kuba@...nel.org>

Thanks!