Re: [PATCH v4] net: make get_net_ns return error if NET_NS is disabled

[Christian Brauner]

On Fri, Jun 11, 2021 at 10:29:59PM +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.
> 
> Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
> Fixes: c62cce2caee5 ("net: add an ioctl to get a socket network namespace")
> Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: David Laight <David.Laight@xxxxxxxxxx>
> Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
> Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>

Looks good,
Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>