openrisc: fix copy_from_user()

... that should zero on faults.  Also remove the <censored> helpful
logics wrt range truncation copied from ppc32.  Where it had ever
been needed only in case of copy_from_user() *and* had not been merged
into the mainline until a month after the need had disappeared.
A decade before openrisc went into mainline, I might add...

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 24 deletions

diff --git a/arch/openrisc/include/asm/uaccess.h b/arch/openrisc/include/asm/uaccess.h
index a6bd07ca3d6c..cbad29b5a131 100644
--- a/arch/openrisc/include/asm/uaccess.h
+++ b/arch/openrisc/include/asm/uaccess.h
@@ -273,28 +273,20 @@ __copy_tofrom_user(void *to, const void *from, unsigned long size);
 static inline unsigned long
 copy_from_user(void *to, const void *from, unsigned long n)
 {
-        unsigned long over;
-
-        if (access_ok(VERIFY_READ, from, n))
-                return __copy_tofrom_user(to, from, n);
-        if ((unsigned long)from < TASK_SIZE) {
-                over = (unsigned long)from + n - TASK_SIZE;
-                return __copy_tofrom_user(to, from, n - over) + over;
-        }
-        return n;
+        unsigned long res = n;
+
+        if (likely(access_ok(VERIFY_READ, from, n)))
+                n = __copy_tofrom_user(to, from, n);
+        if (unlikely(res))
+                memset(to + (n - res), 0, res);
+        return res;
 }
 
 static inline unsigned long
 copy_to_user(void *to, const void *from, unsigned long n)
 {
-        unsigned long over;
-
-        if (access_ok(VERIFY_WRITE, to, n))
-                return __copy_tofrom_user(to, from, n);
-        if ((unsigned long)to < TASK_SIZE) {
-                over = (unsigned long)to + n - TASK_SIZE;
-                return __copy_tofrom_user(to, from, n - over) + over;
-        }
+        if (likely(access_ok(VERIFY_WRITE, to, n)))
+                n = __copy_tofrom_user(to, from, n);
         return n;
 }
 
@@ -303,13 +295,8 @@ extern unsigned long __clear_user(void *addr, unsigned long size);
 static inline __must_check unsigned long
 clear_user(void *addr, unsigned long size)
 {
-
-        if (access_ok(VERIFY_WRITE, addr, size))
-                return __clear_user(addr, size);
-        if ((unsigned long)addr < TASK_SIZE) {
-                unsigned long over = (unsigned long)addr + size - TASK_SIZE;
-                return __clear_user(addr, size - over) + over;
-        }
+        if (likely(access_ok(VERIFY_WRITE, addr, size)))
+                size = __clear_user(addr, size);
         return size;
 }