From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: [RFC ] netlink: limit large vmalloc() based skbs to NETLINK_NETFILTER Date: Tue, 2 Jul 2013 23:50:15 +0200 Message-ID: <20130702215015.GA1979@breakpoint.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Patrick McHardy , netdev@vger.kernel.org, Dave Jones To: Pablo Neira Ayuso Return-path: Received: from Chamillionaire.breakpoint.cc ([80.244.247.6]:48363 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755105Ab3GBVuW (ORCPT ); Tue, 2 Jul 2013 17:50:22 -0400 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Since commit c05cdb1b ("netlink: allow large data transfers from user-space") the large skbs are allocated via vmalloc(). Trinity triggered this in response: | BUG: unable to handle kernel paging request at ffffc900001bf001 | IP: [] skb_clone+0x1a/0xa0 | Call Trace: | [] nl_fib_input+0x37/0x230 | [] ? _raw_read_unlock+0x22/0x40 | [] netlink_unicast+0x13a/0x1f0 | [] netlink_sendmsg+0x327/0x420 The problem is that the vmalloc() based skb ends exactly at size (where ->end is pointing) and skb_shinfo() starts past ->end where we have our guard page and hence we BUG(). The question is should we fix this or forbid the skb_clone(). Fixing this behaviour is tricky because even after we add space for struct skb_shared_info we release the memory from the destructor so once the first skbs is gone, the memory in the clone is invalid. The other case where skb_clone() is used is when we have mutltiple destinations. Since I assume the initial target was to extend the size for NETLINK_NETFILTER this patch limits to this target only and with single destination. Is this okay? Signed-off-by: Sebastian Andrzej Siewior --- net/netlink/af_netlink.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 68c1673..9926453 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2129,7 +2129,11 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock, if (len > sk->sk_sndbuf - 32) goto out; err = -ENOBUFS; - skb = netlink_alloc_large_skb(len); + if (netlink_is_kernel(sk) && sk->sk_protocol == NETLINK_NETFILTER && + !dst_group) + skb = netlink_alloc_large_skb(len); + else + skb = alloc_skb(len, GFP_KERNEL); if (skb == NULL) goto out; -- 1.8.3.1