linux-kernel - Re: [PATCH rdma-next 3/4] gcov: Protect from uninitialized number of functions provided by GCC 10.2

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Message-ID: <CAHk-=wiLHGi31Mpc6ObCYD8ho8Yy=0UqGyo6E_Ocv4XaFcEkKA@mail.gmail.com>
Date:   Wed, 2 Sep 2020 10:41:21 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Colin Ian King <colin.king@...onical.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH rdma-next 3/4] gcov: Protect from uninitialized number of
 functions provided by GCC 10.2

On Wed, Sep 2, 2020 at 1:55 AM Leon Romanovsky <leon@...nel.org> wrote:
>
> This trace is seen because n_function value provided by GCC through
> __gcov_init() is ridiculously high, in my case it was 2698213824,
> which probably means that the field is not initialized.

This seems to be wrong - since a different (smaller) uninitialized
value will succeed in the kcalloc, but will then walk some random
array size when copying and fail later instead.

So this doesn't actually seem to _fix_ anything, it just hides one
special case of bogus values.

              Linus