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SubjectRe: [PATCH v2] [PATCH] KEYS: trusted: fix -Wvarags warning
On Mon, Oct 22, 2018 at 04:43:57PM -0700, ndesaulniers@google.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@aculab.com>
> Suggested-by: Denis Kenzior <denkenz@gmail.com>
> Suggested-by: James Bottomley <jejb@linux.vnet.ibm.com>
> Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> v1 -> v2:
> * Don't reorder args, just use default function promotion type
> of unsigned int.
> * Add !! boolean cast as per Denis in
> https://lkml.org/lkml/2018/10/12/838.
> * Tested with gcc-8 and clang-8.
>
> include/keys/trusted.h | 2 +-
> security/keys/trusted.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/keys/trusted.h b/include/keys/trusted.h
> index adbcb6817826..0071298b9b28 100644
> --- a/include/keys/trusted.h
> +++ b/include/keys/trusted.h
> @@ -38,7 +38,7 @@ enum {
>
> int TSS_authhmac(unsigned char *digest, const unsigned char *key,
> unsigned int keylen, unsigned char *h1,
> - unsigned char *h2, unsigned char h3, ...);
> + unsigned char *h2, unsigned int h3, ...);
> int TSS_checkhmac1(unsigned char *buffer,
> const uint32_t command,
> const unsigned char *ononce,
> diff --git a/security/keys/trusted.c b/security/keys/trusted.c
> index ff6789365a12..335ce6d1cf6b 100644
> --- a/security/keys/trusted.c
> +++ b/security/keys/trusted.c
> @@ -123,7 +123,7 @@ static int TSS_rawhmac(unsigned char *digest, const unsigned char *key,
> */
> int TSS_authhmac(unsigned char *digest, const unsigned char *key,
> unsigned int keylen, unsigned char *h1,
> - unsigned char *h2, unsigned char h3, ...)
> + unsigned char *h2, unsigned int h3, ...)
> {
> unsigned char paramdigest[SHA1_DIGEST_SIZE];
> struct sdesc *sdesc;
> @@ -139,7 +139,7 @@ int TSS_authhmac(unsigned char *digest, const unsigned char *key,
> return PTR_ERR(sdesc);
> }
>
> - c = h3;
> + c = !!h3;
> ret = crypto_shash_init(&sdesc->shash);
> if (ret < 0)
> goto out;
> --
> 2.19.1.568.g152ad8e336-goog
>

Thank you for the fix!
Nathan

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