linux-kernel - Re: [PATCH v2 bpf-next] libbpf: Fix signed overflow in ringbuf_process

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Message-ID: <CA+i-1C2+Lt7kmwsZOEw6D8B_Lc+aJdZoUmPDh08+7y_uMNW+kA@mail.gmail.com>
Date:   Mon, 3 May 2021 14:01:00 +0200
From:   Brendan Jackman <jackmanb@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        KP Singh <kpsingh@...nel.org>,
        Florent Revest <revest@...omium.org>
Subject: Re: [PATCH v2 bpf-next] libbpf: Fix signed overflow in ringbuf_process_ring

On Fri, 30 Apr 2021 at 18:31, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
>
> On Thu, Apr 29, 2021 at 6:05 AM Brendan Jackman <jackmanb@...gle.com> wrote:

> > Note: I feel a bit guilty about the fact that this makes the reader
> > think about implicit conversions. Nobody likes thinking about that.
> >
> > But explicit casts don't really help with clarity:
> >
> >   return (int)min(cnt, (int64_t)INT_MAX); // ugh
> >
>
> I'd go with
>
> if (cnt > INT_MAX)
>     return INT_MAX;
>
> return cnt;

Sure, it has all the same implicit casts/promotions but I guess it's
clearer anyway.

> If you don't mind, I can patch it up while applying?

Yes please do, thanks!