Re: PROBLEM: null-ptr deref in ip_options_echo may lead to denial of service
From: Ben Hutchings <hidden>
Date: 2017-03-21 00:34:03
On Sun, 2017-03-19 at 22:25 -0700, Eric Dumazet wrote:
On Mon, 2017-03-20 at 12:59 +0800, Anarcheuz Fritz wrote:quoted
Hi David, While working on some legacy kernel I stumbled upon a null-ptr deref in ip_options_echo. The bug has been verified on the latest version 3.2.87 from the supported long-term branch.Fixed in commit 34b2cef20f19c87999fff3da4071e66937db9644 ("ipv4: keep skb->dst around in presence of IP options") For 3.2, since d826eb14ecef was not backported, following patch should do it. (Bug origin was f84af32cbca70 ("net: ip_queue_rcv_skb() helper"))
I see, I thought the vulnerability was introduced by d826eb14ecef.
quoted hunk ↗ jump to hunk
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index b3648bbef0da..a6e1eeb02267 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c@@ -1009,7 +1009,8 @@ e_inval:*/ int ip_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) { - if (!(inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO)) + if (!(inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO) && + !IPCB(skb)->opt.optlen) skb_dst_drop(skb); return sock_queue_rcv_skb(sk, skb); }
Thanks to both of you; I'll queue this up for 3.2. Ben. -- Ben Hutchings Power corrupts. Absolute power is kind of neat. - John Lehman, Secretary of the US Navy 1981-1987
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