ipv4: try to cache dst_entries which would cause a redirect
Not caching dst_entries which cause redirects could be exploited by hosts
on the same subnet, causing a severe DoS attack. This effect aggravated
since commit f886497212
("ipv4: fix dst race in sk_dst_get()").
Lookups causing redirects will be allocated with DST_NOCACHE set which
will force dst_release to free them via RCU. Unfortunately waiting for
RCU grace period just takes too long, we can end up with >1M dst_entries
waiting to be released and the system will run OOM. rcuos threads cannot
catch up under high softirq load.
Attaching the flag to emit a redirect later on to the specific skb allows
us to cache those dst_entries thus reducing the pressure on allocation
and deallocation.
This issue was discovered by Marcelo Leitner.
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Marcelo Leitner <mleitner@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
412d2907c4
commit
df4d92549f
|
@ -39,11 +39,12 @@ struct inet_skb_parm {
|
|||
struct ip_options opt; /* Compiled IP options */
|
||||
unsigned char flags;
|
||||
|
||||
#define IPSKB_FORWARDED 1
|
||||
#define IPSKB_XFRM_TUNNEL_SIZE 2
|
||||
#define IPSKB_XFRM_TRANSFORMED 4
|
||||
#define IPSKB_FRAG_COMPLETE 8
|
||||
#define IPSKB_REROUTED 16
|
||||
#define IPSKB_FORWARDED BIT(0)
|
||||
#define IPSKB_XFRM_TUNNEL_SIZE BIT(1)
|
||||
#define IPSKB_XFRM_TRANSFORMED BIT(2)
|
||||
#define IPSKB_FRAG_COMPLETE BIT(3)
|
||||
#define IPSKB_REROUTED BIT(4)
|
||||
#define IPSKB_DOREDIRECT BIT(5)
|
||||
|
||||
u16 frag_max_size;
|
||||
};
|
||||
|
|
|
@ -129,7 +129,8 @@ int ip_forward(struct sk_buff *skb)
|
|||
* We now generate an ICMP HOST REDIRECT giving the route
|
||||
* we calculated.
|
||||
*/
|
||||
if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb_sec_path(skb))
|
||||
if (IPCB(skb)->flags & IPSKB_DOREDIRECT && !opt->srr &&
|
||||
!skb_sec_path(skb))
|
||||
ip_rt_send_redirect(skb);
|
||||
|
||||
skb->priority = rt_tos2priority(iph->tos);
|
||||
|
|
|
@ -1554,11 +1554,10 @@ static int __mkroute_input(struct sk_buff *skb,
|
|||
|
||||
do_cache = res->fi && !itag;
|
||||
if (out_dev == in_dev && err && IN_DEV_TX_REDIRECTS(out_dev) &&
|
||||
skb->protocol == htons(ETH_P_IP) &&
|
||||
(IN_DEV_SHARED_MEDIA(out_dev) ||
|
||||
inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res)))) {
|
||||
flags |= RTCF_DOREDIRECT;
|
||||
do_cache = false;
|
||||
}
|
||||
inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res))))
|
||||
IPCB(skb)->flags |= IPSKB_DOREDIRECT;
|
||||
|
||||
if (skb->protocol != htons(ETH_P_IP)) {
|
||||
/* Not IP (i.e. ARP). Do not create route, if it is
|
||||
|
@ -2303,6 +2302,8 @@ static int rt_fill_info(struct net *net, __be32 dst, __be32 src,
|
|||
r->rtm_flags = (rt->rt_flags & ~0xFFFF) | RTM_F_CLONED;
|
||||
if (rt->rt_flags & RTCF_NOTIFY)
|
||||
r->rtm_flags |= RTM_F_NOTIFY;
|
||||
if (IPCB(skb)->flags & IPSKB_DOREDIRECT)
|
||||
r->rtm_flags |= RTCF_DOREDIRECT;
|
||||
|
||||
if (nla_put_be32(skb, RTA_DST, dst))
|
||||
goto nla_put_failure;
|
||||
|
|
Loading…
Reference in a new issue