[IPV4]: Safer reassembly
Another spin of Herbert Xu's "safer ip reassembly" patch
for 2.6.16.
(The original patch is here:
http://marc.theaimsgroup.com/?l=linux-netdev&m=112281936522415&w=2
and my only contribution is to have tested it.)
This patch (optionally) does additional checks before accepting IP
fragments, which can greatly reduce the possibility of reassembling
fragments which originated from different IP datagrams.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Arthur Kepner <akepner@sgi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 2fc3fd3..ce5fe3f 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -401,6 +401,7 @@
return NULL;
n->v4daddr = daddr;
atomic_set(&n->refcnt, 1);
+ atomic_set(&n->rid, 0);
n->ip_id_count = secure_ip_id(daddr);
n->tcp_ts_stamp = 0;
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 8ce0ce2..ce2b70c 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -22,6 +22,7 @@
* Patrick McHardy : LRU queue of frag heads for evictor.
*/
+#include <linux/compiler.h>
#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
@@ -38,6 +39,7 @@
#include <net/ip.h>
#include <net/icmp.h>
#include <net/checksum.h>
+#include <net/inetpeer.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/inet.h>
@@ -56,6 +58,8 @@
int sysctl_ipfrag_high_thresh = 256*1024;
int sysctl_ipfrag_low_thresh = 192*1024;
+int sysctl_ipfrag_max_dist = 64;
+
/* Important NOTE! Fragment queue must be destroyed before MSL expires.
* RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
*/
@@ -89,8 +93,10 @@
spinlock_t lock;
atomic_t refcnt;
struct timer_list timer; /* when will this queue expire? */
- int iif;
struct timeval stamp;
+ int iif;
+ unsigned int rid;
+ struct inet_peer *peer;
};
/* Hash table. */
@@ -195,6 +201,9 @@
BUG_TRAP(qp->last_in&COMPLETE);
BUG_TRAP(del_timer(&qp->timer) == 0);
+ if (qp->peer)
+ inet_putpeer(qp->peer);
+
/* Release all fragment data. */
fp = qp->fragments;
while (fp) {
@@ -353,6 +362,7 @@
qp->meat = 0;
qp->fragments = NULL;
qp->iif = 0;
+ qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
/* Initialize a timer for this entry. */
init_timer(&qp->timer);
@@ -398,6 +408,56 @@
return ip_frag_create(hash, iph, user);
}
+/* Is the fragment too far ahead to be part of ipq? */
+static inline int ip_frag_too_far(struct ipq *qp)
+{
+ struct inet_peer *peer = qp->peer;
+ unsigned int max = sysctl_ipfrag_max_dist;
+ unsigned int start, end;
+
+ int rc;
+
+ if (!peer || !max)
+ return 0;
+
+ start = qp->rid;
+ end = atomic_inc_return(&peer->rid);
+ qp->rid = end;
+
+ rc = qp->fragments && (end - start) > max;
+
+ if (rc) {
+ IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
+ }
+
+ return rc;
+}
+
+static int ip_frag_reinit(struct ipq *qp)
+{
+ struct sk_buff *fp;
+
+ if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time)) {
+ atomic_inc(&qp->refcnt);
+ return -ETIMEDOUT;
+ }
+
+ fp = qp->fragments;
+ do {
+ struct sk_buff *xp = fp->next;
+ frag_kfree_skb(fp, NULL);
+ fp = xp;
+ } while (fp);
+
+ qp->last_in = 0;
+ qp->len = 0;
+ qp->meat = 0;
+ qp->fragments = NULL;
+ qp->iif = 0;
+
+ return 0;
+}
+
/* Add new segment to existing queue. */
static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
{
@@ -408,6 +468,12 @@
if (qp->last_in & COMPLETE)
goto err;
+ if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
+ unlikely(ip_frag_too_far(qp)) && unlikely(ip_frag_reinit(qp))) {
+ ipq_kill(qp);
+ goto err;
+ }
+
offset = ntohs(skb->nh.iph->frag_off);
flags = offset & ~IP_OFFSET;
offset &= IP_OFFSET;
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index eba64e2..2a830de 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -445,6 +445,7 @@
hlen = iph->ihl * 4;
mtu = dst_mtu(&rt->u.dst) - hlen; /* Size of data space */
+ IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
/* When frag_list is given, use it. First, check its validity:
* some transformers could create wrong frag_list or break existing
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 01444a0..dbf8295 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -22,6 +22,7 @@
extern int sysctl_ip_nonlocal_bind;
#ifdef CONFIG_SYSCTL
+static int zero;
static int tcp_retr1_max = 255;
static int ip_local_port_range_min[] = { 1, 1 };
static int ip_local_port_range_max[] = { 65535, 65535 };
@@ -614,6 +615,15 @@
.strategy = &sysctl_jiffies
},
{
+ .ctl_name = NET_IPV4_IPFRAG_MAX_DIST,
+ .procname = "ipfrag_max_dist",
+ .data = &sysctl_ipfrag_max_dist,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .extra1 = &zero
+ },
+ {
.ctl_name = NET_TCP_NO_METRICS_SAVE,
.procname = "tcp_no_metrics_save",
.data = &sysctl_tcp_nometrics_save,
