From: Al Viro <viro@zeniv.linux.org.uk>
Date: Thu, 18 Aug 2016 03:19:01 +0000 (-0400)
Subject: asm-generic: make get_user() clear the destination on errors
X-Git-Tag: v4.14-rc1~2493^2~25
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9ad18b75c2f6e4a78ce204e79f37781f8815c0fa;p=platform%2Fkernel%2Flinux-rpi.git

asm-generic: make get_user() clear the destination on errors

both for access_ok() failures and for faults halfway through

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

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index 04e21a41796a..32901d11f8c4 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -230,14 +230,18 @@ extern int __put_user_bad(void) __attribute__((noreturn));
 	might_fault();						\
 	access_ok(VERIFY_READ, __p, sizeof(*ptr)) ?		\
 		__get_user((x), (__typeof__(*(ptr)) *)__p) :	\
-		-EFAULT;					\
+		((x) = (__typeof__(*(ptr)))0,-EFAULT);		\
 })
 
 #ifndef __get_user_fn
 static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
 {
-	size = __copy_from_user(x, ptr, size);
-	return size ? -EFAULT : size;
+	size_t n = __copy_from_user(x, ptr, size);
+	if (unlikely(n)) {
+		memset(x + (size - n), 0, n);
+		return -EFAULT;
+	}
+	return 0;
 }
 
 #define __get_user_fn(sz, u, k)	__get_user_fn(sz, u, k)