Re: [PATCH] net/core/dev_ioctl: avoid invoking modprobe with empty ifr_name

[Paolo Abeni]

On 11/17/24 05:55, Song Chen wrote:
> dev_ioctl handles requests from user space if a process calls
> ioctl(sockfd, SIOCGIFINDEX, &ifr). However, if this user space
> process doesn't have interface name well specified, dev_ioctl
> doesn't give it an essential check, as a result, dev_load will
> invoke modprobe with a nonsense module name if the user happens
> to be sys admin or root, see following code in dev_load:
> 
>     no_module = !dev;
>     if (no_module && capable(CAP_NET_ADMIN))
>         no_module = request_module("netdev-%s", name);
>     if (no_module && capable(CAP_SYS_MODULE))
>         request_module("%s", name);
> 
> This patch checks if ifr_name is empty at the beginning, reduces
> the overhead of calling modprobe.

AFAICS technically this optimize a slow path (bad input from the
user-space) at the expense of the more usual path (additional unneeded
conditional) and still AFAICS, there are no functional issues addressed
here.

Note that even the latter more usual path is not a fast path, still the
optimization is not worthy.

/P