From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net-next-2.6] netlink: netlink_recvmsg() fix Date: Tue, 20 Jul 2010 15:16:29 +0200 Message-ID: <1279631789.2498.71.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , Johannes Berg To: David Miller Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:41240 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750786Ab0GTNQd (ORCPT ); Tue, 20 Jul 2010 09:16:33 -0400 Received: by wwj40 with SMTP id 40so829141wwj.1 for ; Tue, 20 Jul 2010 06:16:32 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Please note following potential bug was discovered by code review, and my patch not even tested, please double check ! Thanks [PATCH net-next-2.6] netlink: netlink_recvmsg() fix commit 1dacc76d0014 (net/compat/wext: send different messages to compat tasks) introduced a race condition on netlink, in case MSG_PEEK is used. An skb given by skb_recv_datagram() might be shared, we must clone it before any modification, or risk fatal corruption. Signed-off-by: Eric Dumazet --- net/netlink/af_netlink.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 7aeaa83..dad5e81 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1405,7 +1405,7 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock, struct netlink_sock *nlk = nlk_sk(sk); int noblock = flags&MSG_DONTWAIT; size_t copied; - struct sk_buff *skb, *frag __maybe_unused = NULL; + struct sk_buff *skb; int err; if (flags&MSG_OOB) @@ -1440,8 +1440,17 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock, kfree_skb(skb); skb = compskb; } else { - frag = skb_shinfo(skb)->frag_list; - skb_shinfo(skb)->frag_list = NULL; + struct sk_buff *nskb = skb_clone(skb, GFP_KERNEL); + + if (!nskb) { + skb_free_datagram(sk, skb); + err = -ENOMEM; + goto out; + } + kfree_skb(skb); + kfree_skb(skb_shinfo(nskb)->frag_list); + skb_shinfo(nskb)->frag_list = NULL; + skb = nskb; } } #endif @@ -1477,10 +1486,6 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock, if (flags & MSG_TRUNC) copied = skb->len; -#ifdef CONFIG_COMPAT_NETLINK_MESSAGES - skb_shinfo(skb)->frag_list = frag; -#endif - skb_free_datagram(sk, skb); if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2)