Prevent PacketBuffers from being returned to the pool too early in nic.
Prevent PacketBuffers from being returned to the pool too early in nic.

PacketBuffers were calling DecRef inside the forEach callback in
deliverOutboundPacket and DeliverNetworkPacket, even though
they were referenced in future iterations of the loop. This caused a
data race.

Reported-by: 8f0c6911932c211198a39a559677e890cac12ecd@syzkaller.appspotmail.com
PiperOrigin-RevId: 408972907

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor