On Sat, 29 May 2021 14:05:26 +0800 Changbin Du wrote: > When NET_NS is not enabled, socket ioctl cmd SIOCGSKNS should do nothing > but acknowledge userspace it is not supported. Otherwise, kernel would > panic wherever nsfs trys to access ns->ops since 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 > > Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # v4.9 Please provide a Fixes tag. > diff --git a/net/socket.c b/net/socket.c > index 27e3e7d53f8e..644b46112d35 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg) > mutex_unlock(&vlan_ioctl_mutex); > break; > case SIOCGSKNS: > +#ifdef CONFIG_NET_NS > err = -EPERM; > if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) > break; > > err = open_related_ns(&net->ns, get_net_ns); There's a few more places with this exact code. Can we please add the check in get_net_ns? That should fix all callers. > +#else > + err = -ENOTSUPP; EOPNOTSUPP, you shouldn't return ENOTSUPP to user space. > +#endif > break; > case SIOCGSTAMP_OLD: > case SIOCGSTAMPNS_OLD:
