On Fri, 9 Sept 2022 at 09:38, Marco Elver elver@google.com wrote:

With Clang version 16+, -fsanitize=thread will turn memcpy/memset/memmove calls in instrumented functions into __tsan_memcpy/__tsan_memset/__tsan_memmove calls respectively.

Add these functions to the core KCSAN runtime, so that we (a) catch data races with mem* functions, and (b) won't run into linker errors with such newer compilers.

Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Marco Elver elver@google.com

---

v2:

• Fix for architectures which do not provide their own memcpy/memset/memmove and instead use the generic versions in lib/string. In this case we'll just alias the __tsan_ variants.

---

kernel/kcsan/core.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index fe12dfe254ec..4015f2a3e7f6 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -18,6 +18,7 @@ #include <linux/percpu.h> #include <linux/preempt.h> #include <linux/sched.h> +#include <linux/string.h> #include <linux/uaccess.h>

#include "encoding.h" @@ -1308,3 +1309,41 @@ noinline void __tsan_atomic_signal_fence(int memorder) } } EXPORT_SYMBOL(__tsan_atomic_signal_fence);

+#ifdef __HAVE_ARCH_MEMSET +void *__tsan_memset(void *s, int c, size_t count); +noinline void *__tsan_memset(void *s, int c, size_t count) +{

•   check_access(s, count, KCSAN_ACCESS_WRITE, _RET_IP_);
  

These can use large sizes, does it make sense to truncate it to MAX_ENCODABLE_SIZE?

•   return __memset(s, c, count);
  

+} +#else +void *__tsan_memset(void *s, int c, size_t count) __alias(memset); +#endif +EXPORT_SYMBOL(__tsan_memset);

+#ifdef __HAVE_ARCH_MEMMOVE +void *__tsan_memmove(void *dst, const void *src, size_t len); +noinline void *__tsan_memmove(void *dst, const void *src, size_t len) +{

•   check_access(dst, len, KCSAN_ACCESS_WRITE, _RET_IP_);
  

•   check_access(src, len, 0, _RET_IP_);
  

•   return __memmove(dst, src, len);
  

+} +#else +void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove); +#endif +EXPORT_SYMBOL(__tsan_memmove);

+#ifdef __HAVE_ARCH_MEMCPY +void *__tsan_memcpy(void *dst, const void *src, size_t len); +noinline void *__tsan_memcpy(void *dst, const void *src, size_t len) +{

•   check_access(dst, len, KCSAN_ACCESS_WRITE, _RET_IP_);
  

•   check_access(src, len, 0, _RET_IP_);
  

•   return __memcpy(dst, src, len);
  

+} +#else +void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy); +#endif

+EXPORT_SYMBOL(__tsan_memcpy);

2.37.2.789.g6183377224-goog