Re: [PATCH net-next] tcp: fix incorrect parameter validation in the do_tcp_getsockopt() function

[Eric Dumazet]

On Wed, Mar 6, 2024 at 12:57 PM Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
>
> Hello Paolo,
>
> On Wed, Mar 6, 2024 at 7:36 PM Paolo Abeni <pabeni@xxxxxxxxxx> wrote:
> >
> > On Wed, 2024-03-06 at 09:57 +0000, Gavrilov Ilia wrote:
> > > The 'len' variable can't be negative because all 'min_t' parameters
> > > cast to unsigned int, and then the minimum one is chosen.
> >
> > The above is incorrect, as the 'len' variable is a signed integer
>
> The 'len' variable should be converted to the non-negative value as
> this sentence:
>
> len = min_t(unsigned int, len, sizeof(int));
>
> See the comments of min_t(): return minimum of two values, using the
> specified type.
>
> After executing the above code, it doesn't make sense to test if 'len
> < 0', I think.

This is essentially dead (defensive ?) code.

Most compilers optimize this completely, no big deal.