On 06/06/14 17:09, Ben Hutchings wrote:
From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
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 <mst@xxxxxxxxxx>
Acked-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[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 <ben@xxxxxxxxxxxxxxx>
---
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);
Here's the above adjusted for 3.10.42-rc2, builds fine for me with no
warnings, boots and works fine.
--- a/net/core/skbuff.c 2014-06-07 08:17:10.487458236 +0100
+++ b/net/core/skbuff.c 2014-06-07 08:21:18.508991669 +0100
@@ -2844,6 +2844,8 @@
skb_shinfo(nskb)->tx_flags = skb_shinfo(skb)->tx_flags
& SKBTX_SHARED_FRAG;
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);
--
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