udp_tunnel: Add checks for nla_nest_start() in __udp_tunnel_nic_dump_write()

As the nla_nest_start() may fail with NULL returned, the return value
should be checked.

Note that this is not a real bug, nothing will break here.
The next nla_put() will fail as well and we'll bail (and
nla_nest_cancel() can handle NULL). But we keep getting
those "fixes" so whatever.

Signed-off-by: Yuan Can <yuancan@huawei.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20221129013934.55184-1-yuancan@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/udp_tunnel_nic.c b/net/ipv4/udp_tunnel_nic.c
index bc3a043a5d5c7635b7acabe76bb19f7ad59d8db9..029219749785018ae7d3c37a07dd5f4fff44dd01 100644 (file)
--- a/net/ipv4/udp_tunnel_nic.c
+++ b/net/ipv4/udp_tunnel_nic.c
@@ -624,6 +624,8 @@ __udp_tunnel_nic_dump_write(struct net_device *dev, unsigned int table,
                        continue;
 
                nest = nla_nest_start(skb, ETHTOOL_A_TUNNEL_UDP_TABLE_ENTRY);
+               if (!nest)
+                       return -EMSGSIZE;
 
                if (nla_put_be16(skb, ETHTOOL_A_TUNNEL_UDP_ENTRY_PORT,
                                 utn->entries[table][j].port) ||