![Paul Guo](/assets/img/avatar_default.png)
This patch tries to fix the following issue in netfilter: In ip_route_me_harder(), we invoke pskb_expand_head() that rellocates new header with additional head room which can break the alignment of the original packet header. In one of my NAT test case, the NIC port for internal hosts is configured with vlan and the port for external hosts is with general configuration. If we ping an external "unknown" hosts from an internal host, an icmp packet will be sent. We find that in icmp_send()->...->ip_route_me_harder()->pskb_expand_head(), hh_len=18 and current headroom (skb_headroom(skb)) of the packet is 16. After calling pskb_expand_head() the packet header becomes to be unaligned and then our system (arch/tile) panics immediately. Signed-off-by: Paul Guo <ggang@tilera.com> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
250 lines
6.2 KiB
C
250 lines
6.2 KiB
C
/* IPv4 specific functions of netfilter core */
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#include <linux/kernel.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter_ipv4.h>
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#include <linux/ip.h>
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#include <linux/skbuff.h>
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#include <linux/gfp.h>
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#include <linux/export.h>
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#include <net/route.h>
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#include <net/xfrm.h>
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#include <net/ip.h>
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#include <net/netfilter/nf_queue.h>
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/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
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int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
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{
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struct net *net = dev_net(skb_dst(skb)->dev);
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const struct iphdr *iph = ip_hdr(skb);
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struct rtable *rt;
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struct flowi4 fl4 = {};
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__be32 saddr = iph->saddr;
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__u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
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unsigned int hh_len;
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if (addr_type == RTN_UNSPEC)
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addr_type = inet_addr_type(net, saddr);
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if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
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flags |= FLOWI_FLAG_ANYSRC;
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else
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saddr = 0;
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/* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
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* packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
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*/
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fl4.daddr = iph->daddr;
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fl4.saddr = saddr;
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fl4.flowi4_tos = RT_TOS(iph->tos);
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fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
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fl4.flowi4_mark = skb->mark;
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fl4.flowi4_flags = flags;
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rt = ip_route_output_key(net, &fl4);
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if (IS_ERR(rt))
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return -1;
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/* Drop old route. */
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skb_dst_drop(skb);
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skb_dst_set(skb, &rt->dst);
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if (skb_dst(skb)->error)
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return -1;
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#ifdef CONFIG_XFRM
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if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
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xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
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struct dst_entry *dst = skb_dst(skb);
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skb_dst_set(skb, NULL);
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dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
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if (IS_ERR(dst))
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return -1;
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skb_dst_set(skb, dst);
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}
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#endif
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/* Change in oif may mean change in hh_len. */
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hh_len = skb_dst(skb)->dev->hard_header_len;
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if (skb_headroom(skb) < hh_len &&
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pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
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0, GFP_ATOMIC))
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return -1;
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return 0;
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}
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EXPORT_SYMBOL(ip_route_me_harder);
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#ifdef CONFIG_XFRM
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int ip_xfrm_me_harder(struct sk_buff *skb)
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{
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struct flowi fl;
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unsigned int hh_len;
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struct dst_entry *dst;
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if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
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return 0;
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if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
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return -1;
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dst = skb_dst(skb);
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if (dst->xfrm)
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dst = ((struct xfrm_dst *)dst)->route;
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dst_hold(dst);
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dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0);
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if (IS_ERR(dst))
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return -1;
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skb_dst_drop(skb);
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skb_dst_set(skb, dst);
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/* Change in oif may mean change in hh_len. */
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hh_len = skb_dst(skb)->dev->hard_header_len;
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if (skb_headroom(skb) < hh_len &&
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pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
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return -1;
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return 0;
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}
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EXPORT_SYMBOL(ip_xfrm_me_harder);
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#endif
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void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
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EXPORT_SYMBOL(ip_nat_decode_session);
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/*
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* Extra routing may needed on local out, as the QUEUE target never
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* returns control to the table.
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*/
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struct ip_rt_info {
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__be32 daddr;
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__be32 saddr;
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u_int8_t tos;
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u_int32_t mark;
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};
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static void nf_ip_saveroute(const struct sk_buff *skb,
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struct nf_queue_entry *entry)
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{
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struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
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if (entry->hook == NF_INET_LOCAL_OUT) {
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const struct iphdr *iph = ip_hdr(skb);
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rt_info->tos = iph->tos;
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rt_info->daddr = iph->daddr;
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rt_info->saddr = iph->saddr;
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rt_info->mark = skb->mark;
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}
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}
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static int nf_ip_reroute(struct sk_buff *skb,
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const struct nf_queue_entry *entry)
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{
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const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
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if (entry->hook == NF_INET_LOCAL_OUT) {
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const struct iphdr *iph = ip_hdr(skb);
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if (!(iph->tos == rt_info->tos &&
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skb->mark == rt_info->mark &&
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iph->daddr == rt_info->daddr &&
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iph->saddr == rt_info->saddr))
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return ip_route_me_harder(skb, RTN_UNSPEC);
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}
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return 0;
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}
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__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
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unsigned int dataoff, u_int8_t protocol)
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{
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const struct iphdr *iph = ip_hdr(skb);
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__sum16 csum = 0;
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switch (skb->ip_summed) {
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case CHECKSUM_COMPLETE:
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if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
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break;
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if ((protocol == 0 && !csum_fold(skb->csum)) ||
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!csum_tcpudp_magic(iph->saddr, iph->daddr,
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skb->len - dataoff, protocol,
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skb->csum)) {
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skb->ip_summed = CHECKSUM_UNNECESSARY;
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break;
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}
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/* fall through */
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case CHECKSUM_NONE:
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if (protocol == 0)
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skb->csum = 0;
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else
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skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
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skb->len - dataoff,
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protocol, 0);
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csum = __skb_checksum_complete(skb);
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}
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return csum;
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}
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EXPORT_SYMBOL(nf_ip_checksum);
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static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
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unsigned int dataoff, unsigned int len,
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u_int8_t protocol)
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{
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const struct iphdr *iph = ip_hdr(skb);
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__sum16 csum = 0;
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switch (skb->ip_summed) {
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case CHECKSUM_COMPLETE:
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if (len == skb->len - dataoff)
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return nf_ip_checksum(skb, hook, dataoff, protocol);
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/* fall through */
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case CHECKSUM_NONE:
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skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
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skb->len - dataoff, 0);
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skb->ip_summed = CHECKSUM_NONE;
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return __skb_checksum_complete_head(skb, dataoff + len);
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}
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return csum;
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}
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static int nf_ip_route(struct net *net, struct dst_entry **dst,
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struct flowi *fl, bool strict __always_unused)
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{
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struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
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if (IS_ERR(rt))
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return PTR_ERR(rt);
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*dst = &rt->dst;
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return 0;
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}
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static const struct nf_afinfo nf_ip_afinfo = {
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.family = AF_INET,
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.checksum = nf_ip_checksum,
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.checksum_partial = nf_ip_checksum_partial,
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.route = nf_ip_route,
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.saveroute = nf_ip_saveroute,
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.reroute = nf_ip_reroute,
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.route_key_size = sizeof(struct ip_rt_info),
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};
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static int ipv4_netfilter_init(void)
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{
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return nf_register_afinfo(&nf_ip_afinfo);
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}
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static void ipv4_netfilter_fini(void)
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{
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nf_unregister_afinfo(&nf_ip_afinfo);
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}
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module_init(ipv4_netfilter_init);
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module_exit(ipv4_netfilter_fini);
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#ifdef CONFIG_SYSCTL
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struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
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{ .procname = "net", },
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{ .procname = "ipv4", },
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{ .procname = "netfilter", },
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{ }
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};
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EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
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#endif /* CONFIG_SYSCTL */
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