macsec: fix NULL dereference in macsec_upd_offload()

macsec_upd_offload() gets the value of MACSEC_OFFLOAD_ATTR_TYPE
without checking its presence in the request message, and this causes
a NULL dereference. Fix it rejecting any configuration that does not
include this attribute.

Reported-and-tested-by: syzbot+7022ab7c383875c17eff@syzkaller.appspotmail.com
Fixes: dcb780fb2795 ("net: macsec: add nla support for changing the offloading selection")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index da82d7f..0d580d8 100644 (file)
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -2594,6 +2594,9 @@ static int macsec_upd_offload(struct sk_buff *skb, struct genl_info *info)
                return PTR_ERR(dev);
        macsec = macsec_priv(dev);
 
+       if (!tb_offload[MACSEC_OFFLOAD_ATTR_TYPE])
+               return -EINVAL;
+
        offload = nla_get_u8(tb_offload[MACSEC_OFFLOAD_ATTR_TYPE]);
        if (macsec->offload == offload)
                return 0;