On 11/29/2018 04:01 PM, Christoph Paasch wrote:

__qdisc_drop_all() accesses skb->prev to get to the tail of the
segment-list.

With commit 68d2f84a1368 ("net: gro: properly remove skb from list")
the skb-list handling has been changed to set skb->next to NULL and set
the list-poison on skb->prev.

With that change, __qdisc_drop_all() will panic when it tries to
dereference skb->prev.

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks !