From: "Michael S. Tsirkin" <[email protected]> commit 1fd819ecb90cc9b822cd84d3056ddba315d3340f upstream.
skb_segment copies frags around, so we need to copy them carefully to avoid accessing user memory after reporting completion to userspace through a callback. skb_segment doesn't normally happen on datapath: TSO needs to be disabled - so disabling zero copy in this case does not look like a big deal. Signed-off-by: Michael S. Tsirkin <[email protected]> Acked-by: Herbert Xu <[email protected]> Signed-off-by: David S. Miller <[email protected]> [bwh: Backported to 3.2. As skb_segment() only supports page-frags *or* a frag list, there is no need for the additional frag_skb pointer or the preparatory renaming.] Signed-off-by: Ben Hutchings <[email protected]> --- This is what I used in Debian for 3.2, and I believe it applies to all stable branches up to 3.12 inclusive. For branches older than 3.6, this requires cherry-picking commit a353e0ce0fd4 ('skbuff: add an api to orphan frags'). To avoid breaking OOT builds of openvswitch, which will use skb_orphan_frags() if available, it is also necessary to cherry-pick commit dcc0fb782b3a ('skbuff: export skb_copy_ubufs'). Ben. --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2701,6 +2701,9 @@ struct sk_buff *skb_segment(struct sk_bu skb_put(nskb, hsize), hsize); while (pos < offset + len && i < nfrags) { + if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC))) + goto err; + *frag = skb_shinfo(skb)->frags[i]; __skb_frag_ref(frag); size = skb_frag_size(frag); -- Ben Hutchings You can't have everything. Where would you put it?
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