This is a note to let you know that I've just added the patch titled
net: ip_expire() must revalidate route
to the 2.6.38-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-ip_expire-must-revalidate-route.patch
and it can be found in the queue-2.6.38 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 64f3b9e203bd06855072e295557dca1485a2ecba Mon Sep 17 00:00:00 2001
From: Eric Dumazet <[email protected]>
Date: Wed, 4 May 2011 10:02:26 +0000
Subject: net: ip_expire() must revalidate route
From: Eric Dumazet <[email protected]>
commit 64f3b9e203bd06855072e295557dca1485a2ecba upstream.
Commit 4a94445c9a5c (net: Use ip_route_input_noref() in input path)
added a bug in IP defragmentation handling, in case timeout is fired.
When a frame is defragmented, we use last skb dst field when building
final skb. Its dst is valid, since we are in rcu read section.
But if a timeout occurs, we take first queued fragment to build one ICMP
TIME EXCEEDED message. Problem is all queued skb have weak dst pointers,
since we escaped RCU critical section after their queueing. icmp_send()
might dereference a now freed (and possibly reused) part of memory.
Calling skb_dst_drop() and ip_route_input_noref() to revalidate route is
the only possible choice.
Reported-by: Denys Fedoryshchenko <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/ipv4/ip_fragment.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -223,31 +223,30 @@ static void ip_expire(unsigned long arg)
if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
struct sk_buff *head = qp->q.fragments;
+ const struct iphdr *iph;
+ int err;
rcu_read_lock();
head->dev = dev_get_by_index_rcu(net, qp->iif);
if (!head->dev)
goto out_rcu_unlock;
+ /* skb dst is stale, drop it, and perform route lookup again */
+ skb_dst_drop(head);
+ iph = ip_hdr(head);
+ err = ip_route_input_noref(head, iph->daddr, iph->saddr,
+ iph->tos, head->dev);
+ if (err)
+ goto out_rcu_unlock;
+
/*
- * Only search router table for the head fragment,
- * when defraging timeout at PRE_ROUTING HOOK.
+ * Only an end host needs to send an ICMP
+ * "Fragment Reassembly Timeout" message, per RFC792.
*/
- if (qp->user == IP_DEFRAG_CONNTRACK_IN && !skb_dst(head)) {
- const struct iphdr *iph = ip_hdr(head);
- int err = ip_route_input(head, iph->daddr, iph->saddr,
- iph->tos, head->dev);
- if (unlikely(err))
- goto out_rcu_unlock;
-
- /*
- * Only an end host needs to send an ICMP
- * "Fragment Reassembly Timeout" message, per RFC792.
- */
- if (skb_rtable(head)->rt_type != RTN_LOCAL)
- goto out_rcu_unlock;
+ if (qp->user == IP_DEFRAG_CONNTRACK_IN &&
+ skb_rtable(head)->rt_type != RTN_LOCAL)
+ goto out_rcu_unlock;
- }
/* Send an ICMP "Fragment Reassembly Timeout" message. */
icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.38/net-dev_close-should-check-iff_up.patch
queue-2.6.38/net-ip_expire-must-revalidate-route.patch
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