dcache: fix kmemcheck warning in switch_names

commit 08d4f772 upstream.

This patch fixes kmemcheck warning in switch_names. The function
switch_names swaps inline names of two dentries. It swaps full arrays
d_iname, no matter how many bytes are really used by the strings. Reading
data beyond string ends results in kmemcheck warning.

We fix the bug by marking both arrays as fully initialized.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/dcache.c

@@ -2436,6 +2436,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target,
 			 */
 			unsigned int i;
 			BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
+			kmemcheck_mark_initialized(dentry->d_iname, DNAME_INLINE_LEN);
+			kmemcheck_mark_initialized(target->d_iname, DNAME_INLINE_LEN);
 			if (!exchange) {
 				memcpy(dentry->d_iname, target->d_name.name,
 						target->d_name.len + 1);