path: root/net/ipv4/ip_forward.c
diff options
authorHannes Frederic Sowa <hannes@stressinduktion.org>2015-01-23 12:01:26 +0100
committerDavid S. Miller <davem@davemloft.net>2015-01-26 17:28:27 -0800
commitdf4d92549f23e1c037e83323aff58a21b3de7fe0 (patch)
treecb82536dd48281496b6652b628266cdcacffb91d /net/ipv4/ip_forward.c
parent412d2907c41531b60c7ea1f38cfe1116daf2a229 (diff)
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 f88649721268999 ("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>
Diffstat (limited to 'net/ipv4/ip_forward.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index 3a83ce5efa80..787b3c294ce6 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -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))
skb->priority = rt_tos2priority(iph->tos);

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