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From: Arnd Bergmann <arnd@arndb.de>
To: Kees Cook <keescook@chromium.org>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Laura Abbott <labbott@redhat.com>,
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Subject: Re: [PATCH v3 4/5] bug: Provide toggle for BUG on data corruption
Date: Mon, 22 Aug 2016 15:15:35 +0200
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On Wednesday, August 17, 2016 2:42:11 PM CEST Kees Cook wrote:
> +
> +/*
> + * Since detected data corruption should stop operation on the affected
> + * structures, this returns false if the corruption condition is found.
> + */
> +#define CHECK_DATA_CORRUPTION(condition, fmt, ...)                      \
> +       do {                                                             \
> +               if (unlikely(condition)) {                               \
> +                       if (IS_ENABLED(CONFIG_BUG_ON_DATA_CORRUPTION)) { \
> +                               pr_err(fmt, ##__VA_ARGS__);              \
> +                               BUG();                                   \
> +                       } else                                           \
> +                               WARN(1, fmt, ##__VA_ARGS__);             \
> +                       return false;                                    \
> +               }                                                        \
> +       } while (0)
> +

I think the "return false" inside of the macro makes it easy to misread
what is actually going on.

How about making it a macro that returns the condition argument?

#define CHECK_DATA_CORRUPTION(condition, fmt, ...)	\
({	\
	bool _condition = unlikely(condition);	\
	if (_condition) {	\
		...
	}	\
	_condition;	\
})

	Arnd