[PATCH 5.6 07/29] net: fix fraglist segmentation reference count leak

[Greg Kroah-Hartman]

From: Florian Westphal <fw@xxxxxxxxx>

[ Upstream commit cf673ed0e057a2dd68d930c6d7e30d53c70c5789 ]

Xin Long says:
 On udp rx path udp_rcv_segment() may do segment where the frag skbs
 will get the header copied from the head skb in skb_segment_list()
 by calling __copy_skb_header(), which could overwrite the frag skbs'
 extensions by __skb_ext_copy() and cause a leak.

 This issue was found after loading esp_offload where a sec path ext
 is set in the skb.

Fix this by discarding head state of the fraglist skb before replacing
its contents.

Fixes: 3a1296a38d0cf62 ("net: Support GRO/GSO fraglist chaining.")
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Reported-by: Xiumei Mu <xmu@xxxxxxxxxx>
Tested-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Acked-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/skbuff.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3668,6 +3668,7 @@ struct sk_buff *skb_segment_list(struct
 
 		skb_push(nskb, -skb_network_offset(nskb) + offset);
 
+		skb_release_head_state(nskb);
 		 __copy_skb_header(nskb, skb);
 
 		skb_headers_offset_update(nskb, skb_headroom(nskb) - skb_headroom(skb));