From: Peter Oskolkov <posk@xxxxxxxxxx>
[ Upstream commit 7969e5c40dfd04799d4341f1b7cd266b6e47f227 ]
This behavior is required in IPv6, and there is little need
to tolerate overlapping fragments in IPv4. This change
simplifies the code and eliminates potential DDoS attack vectors.
Tested: ran ip_defrag selftest (not yet available uptream).
Suggested-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Peter Oskolkov <posk@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Florian Westphal <fw@xxxxxxxxx>
Acked-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Mao Wenan <maowenan@xxxxxxxxxx>
---
include/uapi/linux/snmp.h | 1 +
net/ipv4/ip_fragment.c | 71 +++++++++++++----------------------------------
net/ipv4/proc.c | 1 +
3 files changed, 21 insertions(+), 52 deletions(-)
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 25a9ad8..9de808e 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -55,6 +55,7 @@ enum
IPSTATS_MIB_ECT1PKTS, /* InECT1Pkts */
IPSTATS_MIB_ECT0PKTS, /* InECT0Pkts */
IPSTATS_MIB_CEPKTS, /* InCEPkts */
+ IPSTATS_MIB_REASM_OVERLAPS, /* ReasmOverlaps */
__IPSTATS_MIB_MAX
};
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 7291565..4e64879 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -342,6 +342,7 @@ static int ip_frag_reinit(struct ipq *qp)
/* Add new segment to existing queue. */
static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
{
+ struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
struct sk_buff *prev, *next;
struct net_device *dev;
unsigned int fragsize;
@@ -422,60 +423,22 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
}
found:
- /* We found where to put this one. Check for overlap with
- * preceding fragment, and, if needed, align things so that
- * any overlaps are eliminated.
+ /* RFC5722, Section 4, amended by Errata ID : 3089
+ * When reassembling an IPv6 datagram, if
+ * one or more its constituent fragments is determined to be an
+ * overlapping fragment, the entire datagram (and any constituent
+ * fragments) MUST be silently discarded.
+ *
+ * We do the same here for IPv4.
*/
- if (prev) {
- int i = (FRAG_CB(prev)->offset + prev->len) - offset;
-
- if (i > 0) {
- offset += i;
- err = -EINVAL;
- if (end <= offset)
- goto err;
- err = -ENOMEM;
- if (!pskb_pull(skb, i))
- goto err;
- if (skb->ip_summed != CHECKSUM_UNNECESSARY)
- skb->ip_summed = CHECKSUM_NONE;
- }
- }
-
- err = -ENOMEM;
+ /* Is there an overlap with the previous fragment? */
+ if (prev &&
+ (FRAG_CB(prev)->offset + prev->len) > offset)
+ goto discard_qp;
- while (next && FRAG_CB(next)->offset < end) {
- int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
-
- if (i < next->len) {
- /* Eat head of the next overlapped fragment
- * and leave the loop. The next ones cannot overlap.
- */
- if (!pskb_pull(next, i))
- goto err;
- FRAG_CB(next)->offset += i;
- qp->q.meat -= i;
- if (next->ip_summed != CHECKSUM_UNNECESSARY)
- next->ip_summed = CHECKSUM_NONE;
- break;
- } else {
- struct sk_buff *free_it = next;
-
- /* Old fragment is completely overridden with
- * new one drop it.
- */
- next = next->next;
-
- if (prev)
- prev->next = next;
- else
- qp->q.fragments = next;
-
- qp->q.meat -= free_it->len;
- sub_frag_mem_limit(qp->q.net, free_it->truesize);
- kfree_skb(free_it);
- }
- }
+ /* Is there an overlap with the next fragment? */
+ if (next && FRAG_CB(next)->offset < end)
+ goto discard_qp;
FRAG_CB(skb)->offset = offset;
@@ -522,6 +485,10 @@ found:
skb_dst_drop(skb);
return -EINPROGRESS;
+discard_qp:
+ ipq_kill(qp);
+ err = -EINVAL;
+ IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
err:
kfree_skb(skb);
return err;
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 3abd9d7..55545d0 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -132,6 +132,7 @@ static const struct snmp_mib snmp4_ipextstats_list[] = {
SNMP_MIB_ITEM("InECT1Pkts", IPSTATS_MIB_ECT1PKTS),
SNMP_MIB_ITEM("InECT0Pkts", IPSTATS_MIB_ECT0PKTS),
SNMP_MIB_ITEM("InCEPkts", IPSTATS_MIB_CEPKTS),
+ SNMP_MIB_ITEM("ReasmOverlaps", IPSTATS_MIB_REASM_OVERLAPS),
SNMP_MIB_SENTINEL
};
--
1.8.3.1
