Moving frags and SKBTX_DEV_ZEROCOPY skbs

[Zoltan Kiss <zoltan.kiss@citrix.com>]

Hi,

Recently I've investigated issues around SKBTX_DEV_ZEROCOPY skbs where 
the frags list were modified. I came across this function skb_shift(), 
which moves frags between skbs. And there are a lot more of such kind, 
skb_split or skb_try_coalesce, for example.
It could be a dangerous thing if a frag is referenced from an skb which 
doesn't have the original destructor_arg, and to avoid that 
skb_orphan_frags should be called. Although probably these functions are 
not normally touched in usual usecases, I think it would be useful to 
review core skb functions proactively and add an skb_orphan_frags 
everywhere where the frags could be referenced from other places.
Any opinion about this?

Regards,

Zoltan