linux-kernel - [PATCH 3.16 277/346] metag: copy_from_user() should zero the destination on access

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Message-ID: <lsq.1479082460.46889786@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "James Hogan" <james.hogan@...tec.com>,
        "Al Viro" <viro@...iv.linux.org.uk>
Subject: [PATCH 3.16 277/346] metag: copy_from_user() should zero the
 destination on access_ok() failure

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit 8ae95ed4ae5fc7c3391ed668b2014c9e2079533b upstream.

Acked-by: James Hogan <james.hogan@...tec.com>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/metag/include/asm/uaccess.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/metag/include/asm/uaccess.h
+++ b/arch/metag/include/asm/uaccess.h
@@ -199,8 +199,9 @@ extern unsigned long __must_check __copy
 static inline unsigned long
 copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	if (access_ok(VERIFY_READ, from, n))
+	if (likely(access_ok(VERIFY_READ, from, n)))
 		return __copy_user_zeroing(to, from, n);
+	memset(to, 0, n);
 	return n;
 }