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SubjectRe: [PATCH v2 4/5] bug: Provide toggle for BUG on data corruption
On Tue, Aug 16, 2016 at 5:26 PM, Joe Perches <joe@perches.com> wrote:
> On Tue, 2016-08-16 at 17:20 -0700, Kees Cook wrote:
>> The kernel checks for cases of data structure corruption under some
>> CONFIGs (e.g. CONFIG_DEBUG_LIST). When corruption is detected, some
>> systems may want to BUG() immediately instead of letting the system run
>> with known corruption. Usually these kinds of manipulation primitives can
>> be used by security flaws to gain arbitrary memory write control. This
>> provides a new config CONFIG_BUG_ON_DATA_CORRUPTION and a corresponding
>> macro CHECK_DATA_CORRUPTION for handling these situations. Notably, even
>> if not BUGing, the kernel should not continue processing the corrupted
>> structure.
> []
>> diff --git a/include/linux/bug.h b/include/linux/bug.h
> []
>> @@ -118,4 +118,21 @@ static inline enum bug_trap_type report_bug(unsigned long bug_addr,
>> }
>>
>> #endif /* CONFIG_GENERIC_BUG */
>> +
>> +/*
>> + * 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, format...) \
>
> My preference would be to use (condition, fmt, ...)
>
>> + do { \
>> + if (unlikely(condition)) { \
>> + if (IS_ENABLED(CONFIG_BUG_ON_DATA_CORRUPTION)) { \
>> + printk(KERN_ERR format); \
>
> and
> pr_err(fmt, ##__VA_ARGS__);
>
> so that any use would also get any local pr_fmt applied as well.
>
>> + BUG(); \
>> + } else \
>> + WARN(1, format); \
>> + return false; \
>> + } \
>> + } while (0)
>> +
>> #endif /* _LINUX_BUG_H */
>

Ah yes, excellent point. I'll convert this for my v3. Thanks!

-Kees

--
Kees Cook
Nexus Security

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