linux-kernel - Re: [PATCH] Support the nonstring variable attribute (gcc >= 8)

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Message-ID: <alpine.DEB.2.10.1802181519400.205822@chino.kir.corp.google.com>
Date:   Sun, 18 Feb 2018 15:20:22 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
cc:     mingo@...nel.org, jpoimboe@...hat.com, keescook@...omium.org,
        akpm@...ux-foundation.org, tglx@...utronix.de,
        geert@...ux-m68k.org, gregkh@...uxfoundation.org,
        thomas.lendacky@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Support the nonstring variable attribute (gcc >= 8)

On Sat, 17 Feb 2018, Miguel Ojeda wrote:

> From the GCC manual:
> 
> The nonstring variable attribute specifies that an object or member
> declaration with type array of char or pointer to char is intended to
> store character arrays that do not necessarily contain a terminating NUL
> character. This is useful in detecting uses of such arrays or pointers
> with functions that expect NUL-terminated strings, and to avoid warnings
> when such an array or pointer is used as an argument to a bounded string
> manipulation function such as strncpy.
> 
>   https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
> 
> Some reports are already coming to the LKML regarding these
> warnings. When they are false positives, we can use __nonstring to let
> gcc know a NUL character is not required; like in this case:
> 
>   https://lkml.org/lkml/2018/1/16/135
> 
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: David Rientjes <rientjes@...gle.com>

I would have expected to have seen __nonstring used somewhere as part of 
this patch.