Re: [PATCH v3] net: make get_net_ns return error if NET_NS is disabled

From: Changbin Du <redacted>
Date: Thu, 10 Jun 2021 23:39:41 +0800

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.

Signed-off-by: Changbin Du <redacted>
Cc: Cong Wang <redacted>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: David Laight <redacted>
Cc: Christian Brauner <redacted>
Suggested-by: Jakub Kicinski <kuba@kernel.org>

As this is a bug fix please rebase on the 'net' tree and provide a proper Fixes: tag.

Thank you.