net: sched: do not requeue a NULL skb

net: sched: do not requeue a NULL skb

Orabug: 25308077

[ Upstream commit 3dcd493fbebfd631913df6e2773cc295d3bf7d22 ]

A failure in validate_xmit_skb_list() triggered an unconditional call
to dev_requeue_skb with skb=NULL. This slowly grows the queue
discipline's qlen count until all traffic through the queue stops.

We take the optimistic approach and continue running the queue after a
failure since it is unknown if later packets also will fail in the
validate path.

Fixes: 55a93b3ea780 ("qdisc: validate skb without holding lock")
Signed-off-by: Lars Persson <larper@axis.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 5730fd5d72071c9ae96929292351029ea56de7c0)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>