RE: [PATCH 1/1] net: ioctl: Use kernel memory on protocol ioctl callbacks

David Laight
2023-05-19T14:22:34Z

From: Breno Leitao
> Sent: 19 May 2023 14:58
>
> Most of the ioctls to net protocols operates directly on userspace
> argument (arg). Usually doing get_user()/put_user() directly in the
> ioctl callback. This is not flexible, because it is hard to reuse these
> functions without passing userspace buffers.
>
> Change the "struct proto" ioctls to avoid touching userspace memory and
> operate on kernel buffers, i.e., all protocol's ioctl callbacks is
> adapted to operate on a kernel memory other than on userspace (so, no
> more {put,get}_user() and friends being called in the ioctl callback).
>
> This changes the "struct proto" ioctl format in the following way:
>
> int (*ioctl)(struct sock *sk, int cmd,
> - unsigned long arg);
> + int *karg);

I think I'd add a karg_len field for the actual buffer length.
It will save embarrassment later on.

Do any of the ioctl functions return +ve values on success?
If not you can use the return value as the length for any
copy_to_user().

If all the current 'cmd' are 16bit, there is the option
of using 32bit IOR() etc commands to get automatic sizing.

David

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