linux-kernel - [PATCH 4.7 170/184] hexagon: fix strncpy_from

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Message-Id: <20160922174055.976438690@linuxfoundation.org>
Date:   Thu, 22 Sep 2016 19:41:44 +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, Richard Kuo <rkuo@...eaurora.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 4.7 170/184] hexagon: fix strncpy_from_user() error return

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

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

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

commit f35c1e0671728d1c9abc405d05ef548b5fcb2fc4 upstream.

It's -EFAULT, not -1 (and contrary to the comment in there,
__strnlen_user() can return 0 - on faults).

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

---
 arch/hexagon/include/asm/uaccess.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -103,7 +103,8 @@ static inline long hexagon_strncpy_from_
 {
 	long res = __strnlen_user(src, n);
 
-	/* return from strnlen can't be zero -- that would be rubbish. */
+	if (unlikely(!res))
+		return -EFAULT;
 
 	if (res > n) {
 		copy_from_user(dst, src, n);