[NETLABEL]: Fix NULL deref in netlbl_unlabel_staticlist_gen() if ifindex not found

dev_get_by_index() may return NULL if nothing is found. In
net/netlabel/netlabel_unlabeled.c::netlbl_unlabel_staticlist_gen() the
function is called, but the return value is never checked. If it returns
NULL then we'll deref a NULL pointer on the very next line.
I checked the callers, and I don't think this can actually happen today,
but code changes over time and in the future it might happen and it does
no harm to be defensive and check for the failure, so that if/when it
happens we'll fail gracefully instead of crashing.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
index a547c6320eb340d0aaa4abdbbd888c0a8f0ae060..d282ad1570a77482a58b836065f79e3ae2714a61 100644 (file)
--- a/net/netlabel/netlabel_unlabeled.c
+++ b/net/netlabel/netlabel_unlabeled.c
@@ -1339,6 +1339,10 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd,
 
        if (iface->ifindex > 0) {
                dev = dev_get_by_index(&init_net, iface->ifindex);
+               if (!dev) {
+                       ret_val = -ENODEV;
+                       goto list_cb_failure;
+               }
                ret_val = nla_put_string(cb_arg->skb,
                                         NLBL_UNLABEL_A_IFACE, dev->name);
                dev_put(dev);