RE: [PATCH v3 5/5] minmax: Relax check to allow comparison between int and small unsigned constants.

David Laight
2023-08-14T15:30:39Z

From: David Laight
> Sent: 14 August 2023 15:51
>
> From: Linus Torvalds <torvalds@linux-foundation.org>
> > Sent: 10 August 2023 20:47
> ...
> > But using an *unsigned* constant 20 when the other side is signed
> > means that now somebody is confused. We should warn.
>
> Then you get 'fixes' like:
>
> int do_tcp_getsockopt(struct sock *sk, int level,
> int optname, sockptr_t optval, sockptr_t optlen)
> {
> struct inet_connection_sock *icsk = inet_csk(sk);
> struct tcp_sock *tp = tcp_sk(sk);
> struct net *net = sock_net(sk);
> int val, len;
>
> if (copy_from_sockptr(&len, optlen, sizeof(int)))
> return -EFAULT;
>
> len = min_t(unsigned int, len, sizeof(int));
>
> if (len < 0)
> return -EINVAL;

Actually that code has been broken since the test was added in 2.4.4.
At that time min() was a local inline with unsigned int args.
2.4.9 added min(type,a,b)
2.4.10 renamed min() to min_t() and added min() with the strict
type checking.

David