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 */
