linux-kernel - RE: [PATCH v2] powerpc/64: Fix build failure with GCC 8.1

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Date:   Tue, 29 May 2018 15:24:21 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christophe LEROY' <christophe.leroy@....fr>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Geoff Levand <geoff@...radead.org>
Subject: RE: [PATCH v2] powerpc/64: Fix build failure with GCC 8.1

From: Christophe LEROY
> Sent: 29 May 2018 10:37
...
> >>>> -       strncpy(new_part->header.name, name, 12);
> >>>> +       memcpy(new_part->header.name, name, strnlen(name,
> >>>> sizeof(new_part->header.name)));
> >>>
> >>>
> >>> The comment for nvram_header.lgnth says:
> >>>
> >>>           /* Terminating null required only for names < 12 chars. */
> >>>
> >>> This will not terminate the string with a zero (the struct is
> >>> allocated with kmalloc).
> >>> So the original code is correct, the new one isn't.
> >>
> >> Right, then I have to first zeroize the destination.
> >
> > Using kzalloc() instead of kmalloc() will do.
> >
> > Still, papering around these warnings seems to obscure things, IMHO.
> > And it increases code size, as you had to add a call to strnlen().
> 
> Right but then, what is the best solution to elimate that warning ?

Time to add the I_really_mean_strncy() function.

	David