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

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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/include/asm-i386/uaccess.h b/include/asm-i386/uaccess.h
index 3f1337c3420..371457b1ceb 100644
--- a/include/asm-i386/uaccess.h
+++ b/include/asm-i386/uaccess.h
@@ -197,13 +197,15 @@ extern void __put_user_8(void);
 
 #define put_user(x,ptr)                                         \
 ({      int __ret_pu;                                           \
+        __typeof__(*(ptr)) __pu_val;                            \
         __chk_user_ptr(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;                                               \
 })