[PATCH v6 04/44] x86: asm: instrument usercopy in get_user() and put_user()

[Alexander Potapenko <glider@google.com>]

Use hooks from instrumented.h to notify bug detection tools about
usercopy events in variations of get_user() and put_user().

Signed-off-by: Alexander Potapenko <glider@google.com>
---
v5:
 -- handle put_user(), make sure to not evaluate pointer/value twice

v6:
 -- add missing empty definitions of instrument_get_user() and
    instrument_put_user()

Link: https://linux-review.googlesource.com/id/Ia9f12bfe5832623250e20f1859fdf5cc485a2fce
---
 arch/x86/include/asm/uaccess.h | 22 +++++++++++++++-------
 include/linux/instrumented.h   | 28 ++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 913e593a3b45f..c1b8982899eca 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -5,6 +5,7 @@
  * User space memory access functions
  */
 #include <linux/compiler.h>
+#include <linux/instrumented.h>
 #include <linux/kasan-checks.h>
 #include <linux/string.h>
 #include <asm/asm.h>
@@ -103,6 +104,7 @@ extern int __get_user_bad(void);
 		     : "=a" (__ret_gu), "=r" (__val_gu),		\
 			ASM_CALL_CONSTRAINT				\
 		     : "0" (ptr), "i" (sizeof(*(ptr))));		\
+	instrument_get_user(__val_gu);					\
 	(x) = (__force __typeof__(*(ptr))) __val_gu;			\
 	__builtin_expect(__ret_gu, 0);					\
 })
@@ -192,9 +194,11 @@ extern void __put_user_nocheck_8(void);
 	int __ret_pu;							\
 	void __user *__ptr_pu;						\
 	register __typeof__(*(ptr)) __val_pu asm("%"_ASM_AX);		\
-	__chk_user_ptr(ptr);						\
-	__ptr_pu = (ptr);						\
-	__val_pu = (x);							\
+	__typeof__(*(ptr)) __x = (x); /* eval x once */			\
+	__typeof__(ptr) __ptr = (ptr); /* eval ptr once */		\
+	__chk_user_ptr(__ptr);						\
+	__ptr_pu = __ptr;						\
+	__val_pu = __x;							\
 	asm volatile("call __" #fn "_%P[size]"				\
 		     : "=c" (__ret_pu),					\
 			ASM_CALL_CONSTRAINT				\
@@ -202,6 +206,7 @@ extern void __put_user_nocheck_8(void);
 		       "r" (__val_pu),					\
 		       [size] "i" (sizeof(*(ptr)))			\
 		     :"ebx");						\
+	instrument_put_user(__x, __ptr, sizeof(*(ptr)));		\
 	__builtin_expect(__ret_pu, 0);					\
 })
 
@@ -248,23 +253,25 @@ extern void __put_user_nocheck_8(void);
 
 #define __put_user_size(x, ptr, size, label)				\
 do {									\
+	__typeof__(*(ptr)) __x = (x); /* eval x once */			\
 	__chk_user_ptr(ptr);						\
 	switch (size) {							\
 	case 1:								\
-		__put_user_goto(x, ptr, "b", "iq", label);		\
+		__put_user_goto(__x, ptr, "b", "iq", label);		\
 		break;							\
 	case 2:								\
-		__put_user_goto(x, ptr, "w", "ir", label);		\
+		__put_user_goto(__x, ptr, "w", "ir", label);		\
 		break;							\
 	case 4:								\
-		__put_user_goto(x, ptr, "l", "ir", label);		\
+		__put_user_goto(__x, ptr, "l", "ir", label);		\
 		break;							\
 	case 8:								\
-		__put_user_goto_u64(x, ptr, label);			\
+		__put_user_goto_u64(__x, ptr, label);			\
 		break;							\
 	default:							\
 		__put_user_bad();					\
 	}								\
+	instrument_put_user(__x, ptr, size);				\
 } while (0)
 
 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
@@ -305,6 +312,7 @@ do {									\
 	default:							\
 		(x) = __get_user_bad();					\
 	}								\
+	instrument_get_user(x);						\
 } while (0)
 
 #define __get_user_asm(x, addr, itype, ltype, label)			\
diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
index ee8f7d17d34f5..9f1dba8f717b0 100644
--- a/include/linux/instrumented.h
+++ b/include/linux/instrumented.h
@@ -153,4 +153,32 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
 {
 }
 
+/**
+ * instrument_get_user() - add instrumentation to get_user()-like macros
+ *
+ * get_user() and friends are fragile, so it may depend on the implementation
+ * whether the instrumentation happens before or after the data is copied from
+ * the userspace.
+ *
+ * @to destination variable, may not be address-taken
+ */
+#define instrument_get_user(to)                         \
+({                                                      \
+})
+
+/**
+ * instrument_put_user() - add instrumentation to put_user()-like macros
+ *
+ * put_user() and friends are fragile, so it may depend on the implementation
+ * whether the instrumentation happens before or after the data is copied from
+ * the userspace.
+ *
+ * @from source address
+ * @ptr userspace pointer to copy to
+ * @size number of bytes to copy
+ */
+#define instrument_put_user(from, ptr, size)                    \
+({                                                              \
+})
+
 #endif /* _LINUX_INSTRUMENTED_H */
-- 
2.37.2.789.g6183377224-goog