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authorMasayuki Nakagawa <nakagawa.msy@ncos.nec.co.jp>2007-01-23 20:15:06 -0800
committerDavid S. Miller <davem@sunset.davemloft.net>2007-01-23 20:25:52 -0800
commitfb7e2399ec17f1004c0e0ccfd17439f8759ede01 (patch)
tree8b63423ad33317dfd2e42fe971a1648db1d60cda /net
parenta6c7ab55dda3e16ab5a3cf6f39585aee5876ac3a (diff)
[TCP]: skb is unexpectedly freed.
I encountered a kernel panic with my test program, which is a very simple IPv6 client-server program. The server side sets IPV6_RECVPKTINFO on a listening socket, and the client side just sends a message to the server. Then the kernel panic occurs on the server. (If you need the test program, please let me know. I can provide it.) This problem happens because a skb is forcibly freed in tcp_rcv_state_process(). When a socket in listening state(TCP_LISTEN) receives a syn packet, then tcp_v6_conn_request() will be called from tcp_rcv_state_process(). If the tcp_v6_conn_request() successfully returns, the skb would be discarded by __kfree_skb(). However, in case of a listening socket which was already set IPV6_RECVPKTINFO, an address of the skb will be stored in treq->pktopts and a ref count of the skb will be incremented in tcp_v6_conn_request(). But, even if the skb is still in use, the skb will be freed. Then someone still using the freed skb will cause the kernel panic. I suggest to use kfree_skb() instead of __kfree_skb(). Signed-off-by: Masayuki Nakagawa <nakagawa.msy@ncos.nec.co.jp> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_input.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c701f6abbfc..5c16e24a606 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4420,9 +4420,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
* But, this leaves one open to an easy denial of
* service attack, and SYN cookies can't defend
* against this problem. So, we drop the data
- * in the interest of security over speed.
+ * in the interest of security over speed unless
+ * it's still in use.
*/
- goto discard;
+ kfree_skb(skb);
+ return 0;
}
goto discard;