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Date: Mon, 22 Aug 2016 15:32:06 -0700
From: Kees Cook <keescook@...omium.org>
To: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Cc: Arnd Bergmann <arnd@...db.de>, 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>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH v3 4/5] bug: Provide toggle for BUG
on data corruption
On Mon, Aug 22, 2016 at 10:53 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> 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?
That's fine with me; it'll require changing the callers of the macros
to test their results, but that should be clean change.
-Kees
--
Kees Cook
Nexus Security
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