skbuff: skb_segment: orphan frags before copying

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@redhat.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index dc4f7683ff52..869c7afe3b07 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2854,6 +2854,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
         skb_frag_t *frag = skb_shinfo(head_skb)->frags;
         unsigned int mss = skb_shinfo(head_skb)->gso_size;
         unsigned int doffset = head_skb->data - skb_mac_header(head_skb);
+        struct sk_buff *frag_skb = head_skb;
         unsigned int offset = doffset;
         unsigned int tnl_hlen = skb_tnl_header_len(head_skb);
         unsigned int headroom;
@@ -2898,6 +2899,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
                         i = 0;
                         nfrags = skb_shinfo(list_skb)->nr_frags;
                         frag = skb_shinfo(list_skb)->frags;
+                        frag_skb = list_skb;
                         pos += skb_headlen(list_skb);
 
                         while (pos < offset + len) {
@@ -2985,6 +2987,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
                                 i = 0;
                                 nfrags = skb_shinfo(list_skb)->nr_frags;
                                 frag = skb_shinfo(list_skb)->frags;
+                                frag_skb = list_skb;
 
                                 BUG_ON(!nfrags);
 
@@ -2999,6 +3002,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
                                 goto err;
                         }
 
+                        if (unlikely(skb_orphan_frags(frag_skb, GFP_ATOMIC)))
+                                goto err;
+
                         *nskb_frag = *frag;
                         __skb_frag_ref(nskb_frag);
                         size = skb_frag_size(nskb_frag);