On Thu, Aug 26, 2021 at 1:59 AM Arnd Bergmann arnd@kernel.org wrote:
On Thu, Aug 26, 2021 at 3:28 AM Peter Collingbourne pcc@google.com wrote:
} else {
} else if (is_dev_ioctl_cmd(cmd)) { struct ifreq ifr; bool need_copyout; if (copy_from_user(&ifr, argp, sizeof(struct ifreq)))@@ -1118,6 +1118,8 @@ static long sock_do_ioctl(struct net *net, struct socket *sock, if (!err && need_copyout) if (copy_to_user(argp, &ifr, sizeof(struct ifreq))) return -EFAULT;
} else {err = -ENOTTY; } return err;} @@ -3306,6 +3308,8 @@ static int compat_ifr_data_ioctl(struct net *net, unsigned int cmd, struct ifreq ifreq; u32 data32;
if (!is_dev_ioctl_cmd(cmd))return -ENOTTY; if (copy_from_user(ifreq.ifr_name, u_ifreq32->ifr_name, IFNAMSIZ)) return -EFAULT; if (get_user(data32, &u_ifreq32->ifr_data))This adds yet another long switch() statement into the socket ioctl case, when there is already one in compat_sock_ioctl_trans(), one in dev_ifsioc() and one in dev_ioctl(), all with roughly the same set of ioctl command codes. If
I think that David's suggestion of using _IOC_TYPE() should be enough to address this for now.
any of them are called frequently, that makes it all even slower, so I wonder if there should be a larger rework altogether. Maybe something based on a single lookup table that we search through directly from sock_ioctl()/compat_sock_ioctl() to deal with the differences in handling (ifreq based, compat handler, proto_ops override, dev_load, rtnl_lock, rcu_read_lock, CAP_NET_ADMIN, copyout, ...).
You are also adding the checks into different places for native and compat mode, which makes them diverge more when we should be trying to make them more common.
I think based on my recent changes, some other simplifications are possible, based on how the compat path already enumerates all the dev ioctls.
I think we should leave that for a followup if still necessary.
Peter