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.
Suggested-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Peter Oskolkov <p...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Florian Westphal <f...@strlen.de>
---
include/uapi/linux/snmp.h | 1 +
net/ipv4/ip_fragment.c | 75 ++++++++++-----------------------------
net/ipv4/proc.c | 1 +
3 files changed, 21 insertions(+), 56 deletions(-)
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index e5ebc83827ab..da1a144f1a51 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -40,6 +40,7 @@ enum
IPSTATS_MIB_REASMREQDS, /* ReasmReqds */
IPSTATS_MIB_REASMOKS, /* ReasmOKs */
IPSTATS_MIB_REASMFAILS, /* ReasmFails */
+ IPSTATS_MIB_REASM_OVERLAPS, /* ReasmOverlaps */
IPSTATS_MIB_FRAGOKS, /* FragOKs */
IPSTATS_MIB_FRAGFAILS, /* FragFails */
IPSTATS_MIB_FRAGCREATES, /* FragCreates */
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index d14d741fb05e..960bf5eab59f 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -277,6 +277,7 @@ 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;
@@ -357,65 +358,23 @@ 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 = (prev->ip_defrag_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;
- }
- }
+ /* Is there an overlap with the previous fragment? */
+ if (prev &&
+ (prev->ip_defrag_offset + prev->len) > offset)
+ goto discard_qp;
- err = -ENOMEM;
-
- while (next && next->ip_defrag_offset < end) {
- int i = end - next->ip_defrag_offset; /* overlap is 'i' bytes */
-
- if (i < next->len) {
- int delta = -next->truesize;
-
- /* Eat head of the next overlapped fragment
- * and leave the loop. The next ones cannot overlap.
- */
- if (!pskb_pull(next, i))
- goto err;
- delta += next->truesize;
- if (delta)
- add_frag_mem_limit(qp->q.net, delta);
- next->ip_defrag_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 && next->ip_defrag_offset < end)
+ goto discard_qp;
/* Note : skb->ip_defrag_offset and skb->dev share the same location */
dev = skb->dev;
@@ -463,6 +422,10 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff
*skb)
skb_dst_drop(skb);
return -EINPROGRESS;
+discard_qp:
+ inet_frag_kill(&qp->q);
+ 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 b46e4cf9a55a..70289682a670 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -119,6 +119,7 @@ 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
};
--
2.18.0.597.ga71716f1ad-goog
