netdev - [PATCH] OOPS with NETLINK_FIB

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Date:	Fri, 21 Dec 2007 12:00:43 +0300
From:	"Denis V. Lunev" <den@...nvz.org>
To:	davem@...emloft.net
Cc:	devel@...nvz.org, netdev@...r.kernel.org, kaber@...sh.net,
	kuznet@....inr.ac.ru
Subject: [PATCH] OOPS with NETLINK_FIB_LOOKUP netlink socket

nl_fib_input re-reuses incoming skb to send the reply. This means that this
packet will be freed twice, namely in:
- netlink_unicast_kernel
- on receive path
Use clone to send as a cure, the caller is responsible for kfree_skb on error.

Thanks to Alexey Dobryan, who originally found the problem.

Signed-off-by: Denis V. Lunev <den@...nvz.org>
---
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index b03c4c6..ac6238a 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -832,10 +832,13 @@ static void nl_fib_input(struct sk_buff *skb)
 
 	nlh = nlmsg_hdr(skb);
 	if (skb->len < NLMSG_SPACE(0) || skb->len < nlh->nlmsg_len ||
-	    nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*frn))) {
-		kfree_skb(skb);
+	    nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*frn)))
 		return;
-	}
+
+	skb = skb_clone(skb, GFP_KERNEL);
+	if (skb == NULL)
+		return;
+	nlh = nlmsg_hdr(skb);
 
 	frn = (struct fib_result_nl *) NLMSG_DATA(nlh);
 	tb = fib_get_table(frn->tb_id_in);
--
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