Merge branch 'net-two-fixes-for-qdisc_pkt_len_init'

Eric Dumazet says:

====================
net: two fixes for qdisc_pkt_len_init()

Inspired by one syzbot report.

At least one qdisc (fq_codel) depends on qdisc_skb_cb(skb)->pkt_len
having a sane value (not zero)

With the help of af_packet, syzbot was able to fool qdisc_pkt_len_init()
to precisely set qdisc_skb_cb(skb)->pkt_len to zero.

First patch fixes this issue.

Second one (a separate one to help future bisections) adds
more sanity check to SKB_GSO_DODGY users.
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>