Re: [PATCH v2] powerpc/64: Fix build failure with GCC 8.1

[Christophe LEROY]

Le 31/05/2018 Ã 07:54, Michael Ellerman a ÃcritÂ:
> Christophe LEROY <christophe.leroy@xxxxxx> writes:
> > Le 29/05/2018 Ã 11:05, Geert Uytterhoeven a ÃcritÂ:
> > > Hi Christophe,
> > > On Tue, May 29, 2018 at 10:56 AM, Christophe LEROY
> > > <christophe.leroy@xxxxxx> wrote:
> > > > Le 29/05/2018 Ã 09:47, Geert Uytterhoeven a Ãcrit :
> > > > > On Tue, May 29, 2018 at 8:03 AM, Christophe Leroy
> > > > > > --- a/arch/powerpc/kernel/nvram_64.c
> > > > > > +++ b/arch/powerpc/kernel/nvram_64.c
> > > > > > @@ -1039,7 +1039,7 @@ loff_t __init nvram_create_partition(const char
> > > > > > *name, int sig,
> > > > > >            new_part->index = free_part->index;
> > > > > >            new_part->header.signature = sig;
> > > > > >            new_part->header.length = size;
> > > > > > -       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().
>
>
> The right fix is to not try and mirror the on-device structure in the
> kernel struct. We should just use a proper NULL terminated string, which
> would avoid the need to explicitly do strncmp(.., .., 12) in the code
> and be less bug prone in general.
>
> The only place where we should need to worry about the 12 byte buffer is
> in nvram_write_header().
>
> Anyway that's a bigger change, so I'll take this for now with kzalloc().

Thanks. You take it as is and add the kzalloc() or you expect a v3 from 
me with the kzalloc()

Christophe