[PATCH 4.4 108/118] asm-generic: make copy_from_user() zero the destination properly

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

--

From: Al Viro 

commit 2545e5da080b4839dd859e3b09343a884f6ab0e3 upstream.

... in all cases, including the failing access_ok()

Note that some architectures using asm-generic/uaccess.h have
__copy_from_user() not zeroing the tail on failure halfway
through.  This variant works either way.

Signed-off-by: Al Viro 
Signed-off-by: Greg Kroah-Hartman 

---
 include/asm-generic/uaccess.h |   10 ++
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -261,11 +261,13 @@ extern int __get_user_bad(void) __attrib
 static inline long copy_from_user(void *to,
const void __user * from, unsigned long n)
 {
+   unsigned long res = n;
might_fault();
-   if (access_ok(VERIFY_READ, from, n))
-   return __copy_from_user(to, from, n);
-   else
-   return n;
+   if (likely(access_ok(VERIFY_READ, from, n)))
+   res = __copy_from_user(to, from, n);
+   if (unlikely(res))
+   memset(to + (n - res), 0, res);
+   return res;
 }
 
 static inline long copy_to_user(void __user *to,

[PATCH 4.4 108/118] asm-generic: make copy_from_user() zero the destination properly

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

--

From: Al Viro 

commit 2545e5da080b4839dd859e3b09343a884f6ab0e3 upstream.

... in all cases, including the failing access_ok()

Note that some architectures using asm-generic/uaccess.h have
__copy_from_user() not zeroing the tail on failure halfway
through.  This variant works either way.

Signed-off-by: Al Viro 
Signed-off-by: Greg Kroah-Hartman 

---
 include/asm-generic/uaccess.h |   10 ++
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -261,11 +261,13 @@ extern int __get_user_bad(void) __attrib
 static inline long copy_from_user(void *to,
const void __user * from, unsigned long n)
 {
+   unsigned long res = n;
might_fault();
-   if (access_ok(VERIFY_READ, from, n))
-   return __copy_from_user(to, from, n);
-   else
-   return n;
+   if (likely(access_ok(VERIFY_READ, from, n)))
+   res = __copy_from_user(to, from, n);
+   if (unlikely(res))
+   memset(to + (n - res), 0, res);
+   return res;
 }
 
 static inline long copy_to_user(void __user *to,