linux-kernel - [PATCH v2 2/3] kcsan: Instrument memcpy/memset/memmove with newer Clang

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Date:   Fri,  9 Sep 2022 09:38:39 +0200
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        llvm@...ts.linux.dev, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-s390@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH v2 2/3] kcsan: Instrument memcpy/memset/memmove with newer Clang

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@...r.kernel.org # v5.10+
Signed-off-by: Marco Elver <elver@...gle.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_);
+	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