Merge branch 'linux-linaro-lsk-v4.1' into linux-linaro-lsk-v4.1-rtlsk-v4.1-16.09-rt

1 files changed, 10 insertions, 2 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 7c2867b44141..167f80e8f08d 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -108,14 +108,22 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
 {
 	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 	struct kobject *kobj = of->kn->parent->priv;
+	size_t len;
 
 	/*
 	 * If buf != of->prealloc_buf, we don't know how
 	 * large it is, so cannot safely pass it to ->show
 	 */
-	if (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
+	if (WARN_ON_ONCE(buf != of->prealloc_buf))
 		return 0;
-	return ops->show(kobj, of->kn->priv, buf);
+	len = ops->show(kobj, of->kn->priv, buf);
+	if (pos) {
+		if (len <= pos)
+			return 0;
+		len -= pos;
+		memmove(buf, buf + pos, len);
+	}
+	return min(count, len);
 }
 
 /* kernfs write callback for regular sysfs files */