[PATCH 3.12 082/111] skbuff: skb_segment: orphan frags before copying

[Jiri Slaby]

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit 1fd819ecb90cc9b822cd84d3056ddba315d3340f ]

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>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 net/core/skbuff.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a12e7da7c7bc..5a60953e6f39 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2731,6 +2731,7 @@ 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;
@@ -2775,6 +2776,7 @@ 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) {
@@ -2869,6 +2871,7 @@ 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);
 
@@ -2883,6 +2886,9 @@ 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);
-- 
2.0.0

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