s390/uaccess: fix possible register corruption in strnlen_user_srst()

The whole point of the out-of-line strnlen_user_srst() function was to
avoid corruption of register 0 due to register asm assignment.
However 'somebody' :) forgot to remove the update_primary_asce() function
call, which may clobber register 0 contents.
So let's remove that call and also move the size check to the calling
function.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c
index 23f866b4c7f1f3564747c8e1251ea3a05bae420d..7416efe8eae419c1249cf60c8f60dc268d1487cc 100644 (file)
--- a/arch/s390/lib/uaccess.c
+++ b/arch/s390/lib/uaccess.c
@@ -338,9 +338,6 @@ static inline unsigned long strnlen_user_srst(const char __user *src,
        register unsigned long reg0 asm("0") = 0;
        unsigned long tmp1, tmp2;
 
-       if (unlikely(!size))
-               return 0;
-       update_primary_asce(current);
        asm volatile(
                "   la    %2,0(%1)\n"
                "   la    %3,0(%0,%1)\n"
@@ -359,6 +356,8 @@ static inline unsigned long strnlen_user_srst(const char __user *src,
 
 unsigned long __strnlen_user(const char __user *src, unsigned long size)
 {
+       if (unlikely(!size))
+               return 0;
        update_primary_asce(current);
        return strnlen_user_srst(src, size);
 }