net: preserve IP control block during GSO segmentation

[ Upstream commit 9207f9d45b0ad071baa128e846d7e7ed85016df3 ]

Skb_gso_segment() uses skb control block during segmentation.
This patch adds 32-bytes room for previous control block which
will be copied into all resulting segments.

This patch fixes kernel crash during fragmenting forwarded packets.
Fragmentation requires valid IP CB in skb for clearing ip options.
Also patch removes custom save/restore in ovs code, now it's redundant.

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Link: http://lkml.kernel.org/r/CALYGNiP-0MZ-FExV2HutTvE9U-QQtkKSoE--KN=JQE5STYsjAA@mail.gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 4398411236f16c3f87691162909dc6197fb62b08..23ce309bd93fbd34f2f484a6368d40ba911f1813 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3437,7 +3437,8 @@ struct skb_gso_cb {
        int     encap_level;
        __u16   csum_start;
 };
-#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb)
+#define SKB_SGO_CB_OFFSET      32
+#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_SGO_CB_OFFSET))
 
 static inline int skb_tnl_header_len(const struct sk_buff *inner_skb)
 {

diff --git a/net/core/dev.c b/net/core/dev.c
index c14748d051e7f58343768e920e52317154ef06fb..6369c456e3262226667821761ddf96a6c819a548 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2539,6 +2539,8 @@ static inline bool skb_needs_check(struct sk_buff *skb, bool tx_path)
  *
  *     It may return NULL if the skb requires no segmentation.  This is
  *     only possible when GSO is used for verifying header integrity.
+ *
+ *     Segmentation preserves SKB_SGO_CB_OFFSET bytes of previous skb cb.
  */
 struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
                                  netdev_features_t features, bool tx_path)
@@ -2553,6 +2555,9 @@ struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
                        return ERR_PTR(err);
        }
 
+       BUILD_BUG_ON(SKB_SGO_CB_OFFSET +
+                    sizeof(*SKB_GSO_CB(skb)) > sizeof(skb->cb));
+
        SKB_GSO_CB(skb)->mac_offset = skb_headroom(skb);
        SKB_GSO_CB(skb)->encap_level = 0;
 

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 314f26e9e607ea882ed968ed2729008a85cf882d..b945f1e9d7bac61026658856a8383a95e209a670 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -240,6 +240,7 @@ static int ip_finish_output_gso(struct sock *sk, struct sk_buff *skb,
         * from host network stack.
         */
        features = netif_skb_features(skb);
+       BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
        segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
        if (IS_ERR_OR_NULL(segs)) {
                kfree_skb(skb);

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index c5d08ee377304313e7e320133e46343adff5da95..6e9a2220939d74a5f654aa093df900dff87911cd 100644 (file)
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -337,12 +337,10 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
        unsigned short gso_type = skb_shinfo(skb)->gso_type;
        struct sw_flow_key later_key;
        struct sk_buff *segs, *nskb;
-       struct ovs_skb_cb ovs_cb;
        int err;
 
-       ovs_cb = *OVS_CB(skb);
+       BUILD_BUG_ON(sizeof(*OVS_CB(skb)) > SKB_SGO_CB_OFFSET);
        segs = __skb_gso_segment(skb, NETIF_F_SG, false);
-       *OVS_CB(skb) = ovs_cb;
        if (IS_ERR(segs))
                return PTR_ERR(segs);
        if (segs == NULL)
@@ -360,7 +358,6 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
        /* Queue all of the segments. */
        skb = segs;
        do {
-               *OVS_CB(skb) = ovs_cb;
                if (gso_type & SKB_GSO_UDP && skb != segs)
                        key = &later_key;
 

diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index 68ada2ca4b60707ac70b45aa6f0a9ea142a9dd16..443f78c33de2d142d6e801848baa5bcde02a995c 100644 (file)
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -165,6 +165,8 @@ static int xfrm_output_gso(struct sock *sk, struct sk_buff *skb)
 {
        struct sk_buff *segs;
 
+       BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
+       BUILD_BUG_ON(sizeof(*IP6CB(skb)) > SKB_SGO_CB_OFFSET);
        segs = skb_gso_segment(skb, 0);
        kfree_skb(skb);
        if (IS_ERR(segs))