[PATCH] i386: Add a temporary to make put_user more type safe.

[ebiederm@xmission.com (Eric W. Biederman)]

In some code I am developing I had occasion to change the type of a
variable.  This made the value put_user was putting to user space
wrong.  But the code continued to build cleanly without errors.

Introducing a temporary fixes this problem and at least with gcc-3.3.5
does not cause gcc any problems with optimizing out the temporary.
gcc-4.x using SSA internally ought to be even better at optimizing out
temporaries, so I don't expect a temporary to become a problem.
Especially because in all correct cases the types on both sides of the
assignment to the temporary are the same.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>


---

 include/asm-i386/uaccess.h |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

dd1215e541bfe2ed94a902f7fb263ca44b7e8afa
diff --git a/include/asm-i386/uaccess.h b/include/asm-i386/uaccess.h
index 3f1337c..1641613 100644
--- a/include/asm-i386/uaccess.h
+++ b/include/asm-i386/uaccess.h
@@ -198,12 +198,13 @@ extern void __put_user_8(void);
 #define put_user(x,ptr)						\
 ({	int __ret_pu;						\
 	__chk_user_ptr(ptr);					\
+	__typeof__(*(ptr)) __pu_val = x;			\
 	switch(sizeof(*(ptr))) {				\
-	case 1: __put_user_1(x, ptr); break;			\
-	case 2: __put_user_2(x, ptr); break;			\
-	case 4: __put_user_4(x, ptr); break;			\
-	case 8: __put_user_8(x, ptr); break;			\
-	default:__put_user_X(x, ptr); break;			\
+	case 1: __put_user_1(__pu_val, ptr); break;		\
+	case 2: __put_user_2(__pu_val, ptr); break;		\
+	case 4: __put_user_4(__pu_val, ptr); break;		\
+	case 8: __put_user_8(__pu_val, ptr); break;		\
+	default:__put_user_X(__pu_val, ptr); break;		\
 	}							\
 	__ret_pu;						\
 })
-- 
1.1.5.g3480