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| author |   Hannes Frederic Sowa <hannes@stressinduktion.org> | 2015-01-23 12:01:26 +0100 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2015-01-26 17:28:27 -0800 |
| commit | df4d92549f23e1c037e83323aff58a21b3de7fe0 (patch) | |
| tree | cb82536dd48281496b6652b628266cdcacffb91d /net/ipv4/route.c | |
| parent | Merge branch 'bpf' (diff) | |
| download | linux-dev-df4d92549f23e1c037e83323aff58a21b3de7fe0.tar.xz linux-dev-df4d92549f23e1c037e83323aff58a21b3de7fe0.zip | |
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/route.c')
| -rw-r--r-- | net/ipv4/route.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 6a2155b02602..d58dd0ec3e53 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -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; |