netdev - [PATCH 5/5] skbuff: skb_segment: orphan frags before copying

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Date:	Mon, 10 Mar 2014 19:28:08 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	jbenc@...hat.com, David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Simon Horman <horms@...ge.net.au>,
	Paul Durrant <Paul.Durrant@...rix.com>,
	Thomas Graf <tgraf@...g.ch>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Miklos Szeredi <mszeredi@...e.cz>,
	=?us-ascii?B?PT9VVEYtOD9xP1BldGVyPTIwUGFuPTI4PUU2PUJEPTk4PUU1PThEPUFC?= =?us-ascii?B?PUU1PUI5PUIzPTI5Pz0=?= <panweiping3@...il.com>,
	netdev@...r.kernel.org
Subject: [PATCH 5/5] 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@...hat.com>
---
 net/core/skbuff.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 64ee4e6..ae11f78 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2857,6 +2857,7 @@ 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;
@@ -2901,6 +2902,7 @@ 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) {
@@ -2988,6 +2990,7 @@ 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);
 
@@ -3002,6 +3005,9 @@ 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);
-- 
MST

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