Messages in this thread |  | | Date | Tue, 30 Jan 2018 15:36:10 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v6 0/4] x86, kasan: add KASAN checks to atomic operations |
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Hi Dmitry,
On Mon, Jan 29, 2018 at 06:26:03PM +0100, Dmitry Vyukov wrote: > KASAN uses compiler instrumentation to intercept all memory accesses. > But it does not see memory accesses done in assembly code. > One notable user of assembly code is atomic operations. Frequently, > for example, an atomic reference decrement is the last access to an > object and a good candidate for a racy use-after-free. > > Atomic operations are defined in arch files, but KASAN instrumentation > is required for several archs that support KASAN. Later we will need > similar hooks for KMSAN (uninit use detector) and KTSAN (data race > detector). > > This change introduces wrappers around atomic operations that can be > used to add KASAN/KMSAN/KTSAN instrumentation across several archs, > and adds KASAN checks to them. > > This patch uses the wrappers only for x86 arch. Arm64 will be switched > later. And we also plan to instrument bitops in a similar way.
One way you could reduce the intrusivness for each architecture would be to leave the existing macro names as-is, and redefine them in the asm-generic header. It's certainly ugly, but it makes the porting work a lot smaller. Apologies if you've considered this approach before, but I figured it was worth mentioning just in case.
e.g. for atomic[64]_read, your asm-generic header looks like:
#ifndef _LINUX_ATOMIC_INSTRUMENTED_H #define _LINUX_ATOMIC_INSTRUMENTED_H
#include <linux/build_bug.h> #include <linux/kasan-checks.h>
static __always_inline int __atomic_read_instrumented(const atomic_t *v) { kasan_check_read(v, sizeof(*v)); return atomic_read(v); }
static __always_inline s64 __atomic64_read_instrumented(const atomic64_t *v) { kasan_check_read(v, sizeof(*v)); return atomic64_read(v); }
#undef atomic_read #undef atomic64_read
#define atomic_read __atomic_read_instrumented #define atomic64_read __atomic64_read_instrumented
#endif /* _LINUX_ATOMIC_INSTRUMENTED_H */
and the arch code just includes that in asm/atomic.h once it's done with its definitions.
What do you think? Too stinky?
Will
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