linux-kernel - Re: [PATCH v3 4/5] bug: Provide toggle for BUG on data corruption

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Message-Id: <20160822175307.GI3482@linux.vnet.ibm.com>
Date:   Mon, 22 Aug 2016 10:53:07 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Micay <danielmicay@...il.com>,
        Joe Perches <joe@...ches.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Syed Rameez Mustafa <rameezmustafa@...eaurora.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Jan Kara <jack@...e.cz>, Thomas Gleixner <tglx@...utronix.de>,
        Josef Bacik <jbacik@...com>, Ingo Molnar <mingo@...nel.org>,
        Tejun Heo <tj@...nel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v3 4/5] bug: Provide toggle for BUG on data corruption

On Mon, Aug 22, 2016 at 03:15:35PM +0200, Arnd Bergmann wrote:
> 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;	\
> })

That does look better, now that you mention it.  Kees, any objections?

							Thanx, Paul