[PATCH 4.17 080/101] bpf: sockmap, consume_skb in close path

[Greg Kroah-Hartman]

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

------------------

From: John Fastabend <john.fastabend@xxxxxxxxx>

commit 7ebc14d507b4b55105da8d1a1eda323381529cc7 upstream.

Currently, when a sock is closed and the bpf_tcp_close() callback is
used we remove memory but do not free the skb. Call consume_skb() if
the skb is attached to the buffer.

Reported-by: syzbot+d464d2c20c717ef5a6a8@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 1aa12bdf1bfb ("bpf: sockmap, add sock close() hook to remove socks")
Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/bpf/sockmap.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -471,7 +471,8 @@ static int free_sg(struct sock *sk, int
 	while (sg[i].length) {
 		free += sg[i].length;
 		sk_mem_uncharge(sk, sg[i].length);
-		put_page(sg_page(&sg[i]));
+		if (!md->skb)
+			put_page(sg_page(&sg[i]));
 		sg[i].length = 0;
 		sg[i].page_link = 0;
 		sg[i].offset = 0;
@@ -480,6 +481,8 @@ static int free_sg(struct sock *sk, int
 		if (i == MAX_SKB_FRAGS)
 			i = 0;
 	}
+	if (md->skb)
+		consume_skb(md->skb);
 
 	return free;
 }