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Note that pktgen is not available to > >> unprivileged users, so it's a less severe bug. > >> > >> The patch also makes ip6_tnl_xmit() consistent with its IPv4 counterpart > >> (ip_tunnel_xmit()) which is already using skb_cow_head(). > >> > >> Zhiling, please add a note in the commit message that ip6gretap and > >> ip6erspan do not expect to be handed shared skbs given that they clear > >> IFF_TX_SKB_SHARING. > > > > Thanks, Ido. I'll add a note to the commit message explaining that > > ip6gretap and ip6erspan clear IFF_TX_SKB_SHARING and therefore do not > > expect shared skbs, and send a v2 with your Reviewed-by tag retained. > > I'm not sure if it's too late, but since a v2 is required, I think it > would be better to keep the skb_shared check: that will avoid a later > patch for the pktgen/shared issue that inevitably will land, possibly > via the security channel. What do you mean by "keep the skb_shared check"? Return an error if the skb is shared before calling skb_cow_head()? How would that avoid "a later patch for the pktgen/shared issue" when other tunnels are already calling skb_cow_head() without an skb_shared() check (they clear IFF_TX_SKB_SHARING)? Not saying that there isn't a possible problem with pktgen, but it should be fixed there and not papered over in various drivers.