Thank you for the reply. On Wed, Sep 02, 2015 at 11:47:26AM +0200, Daniel Borkmann wrote: > On 09/02/2015 02:04 AM, Ken-ichirou MATSUZAWA wrote: > >Talking about skb_copy path, original skb's shared info is accessed > >only in copy_skb_header, to get gso related field. As a result of > > It's still not correct. The thing is you can neither call skb_copy() nor > skb_clone() on netlink mmaped skbs. For example, skb_copy_bits() would
I am sorry for the lack of explanation. And I am afraid I misunderstand... Updated pointers to its data area in a mmaped netlink skb is only its tail. Head, data and end will not be updated. skb_copy() calls int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) as its argument, "offset" is always 0 and "len" is skb->len. In skb_copy_bits() both "start" and "copy" are skb->len, which means "len - copy" is always 0 so that retuns 0 before accessing shared info. I don't know the situation is intended or not, it seems that skb_copy() for a mmaped skb will not access its shared info. After that, copy_skb_header() will set newly allocate skb's (wrong) gso fields, I asked we should clear it or not. > special case. We need an own netlink_mmap_to_full_skb() handler for this, > that copies/transforms this into a "normal" skb. I'll have a look it this If the above situation is an unintentional, we need it to avoid a future confusion. Thanks, -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html