linux-kernel - [PATCH 4.4 113/118] nios2: copy_from_user() should zero the tail of destination

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Message-Id: <20160922172944.448549955@linuxfoundation.org>
Date:   Thu, 22 Sep 2016 19:30:13 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 4.4 113/118] nios2: copy_from_user() should zero the tail of destination

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

------------------

From: Al Viro <viro@...iv.linux.org.uk>

commit e33d1f6f72cc82fcfc3d1fb20c9e3ad83b1928fa upstream.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/nios2/include/asm/uaccess.h |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/nios2/include/asm/uaccess.h
+++ b/arch/nios2/include/asm/uaccess.h
@@ -102,9 +102,12 @@ extern long __copy_to_user(void __user *
 static inline long copy_from_user(void *to, const void __user *from,
 				unsigned long n)
 {
-	if (!access_ok(VERIFY_READ, from, n))
-		return n;
-	return __copy_from_user(to, from, n);
+	unsigned long res = n;
+	if (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, const void *from,