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authorEric Dumazet <eric.dumazet@gmail.com>2011-05-04 10:02:26 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2011-05-21 15:13:13 -0700
commit4e239472b3bcbc83a4e3115dab5489168d8086fd (patch)
treef6dd137fe661163797788ec7375b9d5152c319e2
parent782cfad3ae0722283b31c747a7f02b974e273f06 (diff)
downloadlinux-2.6.38-lt-ux500-4e239472b3bcbc83a4e3115dab5489168d8086fd.tar.gz
net: ip_expire() must revalidate route
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 <denys@visp.net.lb> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--net/ipv4/ip_fragment.c31
1 files changed, 15 insertions, 16 deletions
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index a1151b8adf3..b1d282f11be 100644
--- 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);