On Wed, 2014-05-14 at 20:41 +0100, Zoltan Kiss wrote: > On 14/05/14 15:23, Eric Dumazet wrote: > > On Wed, 2014-05-14 at 14:40 +0100, Zoltan Kiss wrote: > >> 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? > > > > > > For skb_shift(), it is currently used from tcp stack only, where > > this SKBTX_DEV_ZEROCOPY thing is not used, so I do not think there is a > > bug for the moment. > It is called from tcp_input.c, which suggests it can be called on > incoming TCP packets. Nope. We split outgoing packets, stored in the socket write queue. These packets are locally generated by tcp_sendmsg() and tcp_sendpage(), no way we use SKBTX_DEV_ZEROCOPY yet. This split happens when we receive an ACK, that's why it is in tcp_input.c -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
