net: dsa: avoid potential use-after-free error

If dsa_switch_ops::port_txtstamp() returns false, clone will be freed
immediately. Shouldn't store a pointer to freed memory.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20201119110906.25558-1-ceggers@arri.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index ff2266d..7efc753 100644 (file)
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -522,10 +522,10 @@ static void dsa_skb_tx_timestamp(struct dsa_slave_priv *p,
        if (!clone)
                return;
 
-       DSA_SKB_CB(skb)->clone = clone;
-
-       if (ds->ops->port_txtstamp(ds, p->dp->index, clone, type))
+       if (ds->ops->port_txtstamp(ds, p->dp->index, clone, type)) {
+               DSA_SKB_CB(skb)->clone = clone;
                return;
+       }
 
        kfree_skb(clone);
 }