Messages in this thread | | | From | Kees Cook <> | Date | Tue, 16 Aug 2016 20:39:07 -0700 | Subject | Re: [PATCH v2 4/5] bug: Provide toggle for BUG on data corruption |
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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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