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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> | 2015-01-27 02:28:27 +0100 |
| commit | df4d92549f23e1c037e83323aff58a21b3de7fe0 (patch) | |
| tree | cb82536dd48281496b6652b628266cdcacffb91d /net/ipv4/ip_forward.c | |
| parent | Merge branch 'bpf' (diff) | |
| download | linux-df4d92549f23e1c037e83323aff58a21b3de7fe0.tar.xz linux-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/ip_forward.c')
| -rw-r--r-- | net/ipv4/ip_forward.c | 3 |
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)) ip_rt_send_redirect(skb); skb->priority = rt_tos2priority(iph->tos); |