linux-kernel - Re: [PATCH v2] [PATCH] KEYS: trusted: fix -Wvarags warning

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Message-ID: <alpine.DEB.2.21.1810241136130.3525@jsakkine-mobl1>
Date:   Wed, 24 Oct 2018 11:36:57 +0300 (EEST)
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
cc:     dhowells@...hat.com, jejb@...ux.vnet.ibm.com,
        natechancellor@...il.com, David.Laight@...lab.com,
        denkenz@...il.com,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH v2] [PATCH] KEYS: trusted: fix -Wvarags warning

On Mon, 22 Oct 2018, ndesaulniers@...gle.com wrote:
> Fixes the warning reported by Clang:
> security/keys/trusted.c:146:17: warning: passing an object that
> undergoes default
>      argument promotion to 'va_start' has undefined behavior [-Wvarargs]
>        va_start(argp, h3);
>                       ^
> security/keys/trusted.c:126:37: note: parameter of type 'unsigned
> char' is declared here
> unsigned char *h2, unsigned char h3, ...)
>                               ^
> Specifically, it seems that both the C90 (4.8.1.1) and C11 (7.16.1.4)
> standards explicitly call this out as undefined behavior:
>
> The parameter parmN is the identifier of the rightmost parameter in
> the variable parameter list in the function definition (the one just
> before the ...). If the parameter parmN is declared with ... or with a
> type that is not compatible with the type that results after
> application of the default argument promotions, the behavior is
> undefined.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/41
> Link: https://www.eskimo.com/~scs/cclass/int/sx11c.html
> Suggested-by: David Laight <David.Laight@...lab.com>
> Suggested-by: Denis Kenzior <denkenz@...il.com>
> Suggested-by: James Bottomley <jejb@...ux.vnet.ibm.com>
> Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

/Jarkko