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Subject[PATCH 3.16 274/346] frv: fix clear_user()
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.


From: Al Viro <>

commit 3b8767a8f00cc6538ba6b1cf0f88502e2fd2eb90 upstream.

It should check access_ok(). Otherwise a bunch of places turn into
trivially exploitable rootholes.

Signed-off-by: Al Viro <>
Signed-off-by: Ben Hutchings <>
arch/frv/include/asm/uaccess.h | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

--- a/arch/frv/include/asm/uaccess.h
+++ b/arch/frv/include/asm/uaccess.h
@@ -263,19 +263,25 @@ do { \
extern long __memset_user(void *dst, unsigned long count);
extern long __memcpy_user(void *dst, const void *src, unsigned long count);

-#define clear_user(dst,count) __memset_user(____force(dst), (count))
+#define __clear_user(dst,count) __memset_user(____force(dst), (count))
#define __copy_from_user_inatomic(to, from, n) __memcpy_user((to), ____force(from), (n))
#define __copy_to_user_inatomic(to, from, n) __memcpy_user(____force(to), (from), (n))


-#define clear_user(dst,count) (memset(____force(dst), 0, (count)), 0)
+#define __clear_user(dst,count) (memset(____force(dst), 0, (count)), 0)
#define __copy_from_user_inatomic(to, from, n) (memcpy((to), ____force(from), (n)), 0)
#define __copy_to_user_inatomic(to, from, n) (memcpy(____force(to), (from), (n)), 0)


-#define __clear_user clear_user
+static inline unsigned long __must_check
+clear_user(void __user *to, unsigned long n)
+ if (likely(__access_ok(to, n)))
+ n = __clear_user(to, n);
+ return n;

static inline unsigned long __must_check
__copy_to_user(void __user *to, const void *from, unsigned long n)
 \ /
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