x86: clean up/fix 'copy_in_user()' tail zeroing

[deliverable/linux.git] / arch / x86 / lib / usercopy_64.c

diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index c905e89e19feb5ff79778a11a162dfbaa88852a9..1f33b3d1fd68239c9bb07840d287bcee5d2d26b8 100644 (file)
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -69,21 +69,20 @@ EXPORT_SYMBOL(copy_in_user);
  * it is not necessary to optimize tail handling.
  */
 __visible unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
+copy_user_handle_tail(char *to, char *from, unsigned len)
 {
-       char c;
-       unsigned zero_len;
-
        for (; len; --len, to++) {
+               char c;
+
                if (__get_user_nocheck(c, from++, sizeof(char)))
                        break;
                if (__put_user_nocheck(c, to, sizeof(char)))
                        break;
        }
-
-       for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
-               if (__put_user_nocheck(c, to++, sizeof(char)))
-                       break;
        clac();
+
+       /* If the destination is a kernel buffer, we always clear the end */
+       if ((unsigned long)to >= TASK_SIZE_MAX)
+               memset(to, 0, len);
        return len;
 }