[PATCH 1/2] ip_frag: check fragment length of incoming packet

[Konstantin Ananyev <konstantin.ananyev@intel.com>]

Under some conditions ill-formed fragments might cause
reassembly code to corrupt mbufs and/or crash.
Let say the following fragments sequence:
<ofs=0,len=100, flags=MF>
<ofs=96,len=100, flags=MF>
<ofs=200,len=0,flags=MF>
<ofs=200,len=100,flags=0>
can trigger the problem.
To overcome such situation, added check that fragment length
of incoming value is greater than zero.

Reported-by: <ryan.e.hall@intel.com>
Reported-by: <alexander.v.gutkin@intel.com>

Fixes: 601e279df074 ("ip_frag: move fragmentation/reassembly headers into a library")
Fixes: 4f1a8f633862 ("ip_frag: add IPv6 reassembly")
Cc: stable@dpdk.org

Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
---
 lib/librte_ip_frag/rte_ipv4_reassembly.c | 22 +++++++++++++------
 lib/librte_ip_frag/rte_ipv6_reassembly.c | 28 +++++++++++++++++-------
 2 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/lib/librte_ip_frag/rte_ipv4_reassembly.c b/lib/librte_ip_frag/rte_ipv4_reassembly.c
index 4956b99ea..1029b7abc 100644
--- a/lib/librte_ip_frag/rte_ipv4_reassembly.c
+++ b/lib/librte_ip_frag/rte_ipv4_reassembly.c
@@ -36,8 +36,11 @@ ipv4_frag_reassemble(struct ip_frag_pkt *fp)
 			/* previous fragment found. */
 			if(fp->frags[i].ofs + fp->frags[i].len == ofs) {
 
+				RTE_ASSERT(curr_idx != i);
+
 				/* adjust start of the last fragment data. */
-				rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
+				rte_pktmbuf_adj(m,
+					(uint16_t)(m->l2_len + m->l3_len));
 				rte_pktmbuf_chain(fp->frags[i].mb, m);
 
 				/* this mbuf should not be accessed directly */
@@ -96,14 +99,14 @@ ipv4_frag_reassemble(struct ip_frag_pkt *fp)
  */
 struct rte_mbuf *
 rte_ipv4_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
-		struct rte_ip_frag_death_row *dr, struct rte_mbuf *mb, uint64_t tms,
-		struct ipv4_hdr *ip_hdr)
+	struct rte_ip_frag_death_row *dr, struct rte_mbuf *mb, uint64_t tms,
+	struct ipv4_hdr *ip_hdr)
 {
 	struct ip_frag_pkt *fp;
 	struct ip_frag_key key;
 	const unaligned_uint64_t *psd;
-	uint16_t ip_len;
 	uint16_t flag_offset, ip_ofs, ip_flag;
+	int32_t ip_len;
 
 	flag_offset = rte_be_to_cpu_16(ip_hdr->fragment_offset);
 	ip_ofs = (uint16_t)(flag_offset & IPV4_HDR_OFFSET_MASK);
@@ -116,12 +119,11 @@ rte_ipv4_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
 	key.key_len = IPV4_KEYLEN;
 
 	ip_ofs *= IPV4_HDR_OFFSET_UNITS;
-	ip_len = (uint16_t)(rte_be_to_cpu_16(ip_hdr->total_length) -
-		mb->l3_len);
+	ip_len = rte_be_to_cpu_16(ip_hdr->total_length) - mb->l3_len;
 
 	IP_FRAG_LOG(DEBUG, "%s:%d:\n"
 		"mbuf: %p, tms: %" PRIu64
-		", key: <%" PRIx64 ", %#x>, ofs: %u, len: %u, flags: %#x\n"
+		", key: <%" PRIx64 ", %#x>, ofs: %u, len: %d, flags: %#x\n"
 		"tbl: %p, max_cycles: %" PRIu64 ", entry_mask: %#x, "
 		"max_entries: %u, use_entries: %u\n\n",
 		__func__, __LINE__,
@@ -129,6 +131,12 @@ rte_ipv4_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
 		tbl, tbl->max_cycles, tbl->entry_mask, tbl->max_entries,
 		tbl->use_entries);
 
+	/* check that fragment length is greater then zero. */
+	if (ip_len <= 0) {
+		IP_FRAG_MBUF2DR(dr, mb);
+		return NULL;
+	}
+
 	/* try to find/add entry into the fragment's table. */
 	if ((fp = ip_frag_find(tbl, dr, &key, tms)) == NULL) {
 		IP_FRAG_MBUF2DR(dr, mb);
diff --git a/lib/librte_ip_frag/rte_ipv6_reassembly.c b/lib/librte_ip_frag/rte_ipv6_reassembly.c
index db249fe60..855e3f740 100644
--- a/lib/librte_ip_frag/rte_ipv6_reassembly.c
+++ b/lib/librte_ip_frag/rte_ipv6_reassembly.c
@@ -59,8 +59,11 @@ ipv6_frag_reassemble(struct ip_frag_pkt *fp)
 			/* previous fragment found. */
 			if (fp->frags[i].ofs + fp->frags[i].len == ofs) {
 
+				RTE_ASSERT(curr_idx != i);
+
 				/* adjust start of the last fragment data. */
-				rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
+				rte_pktmbuf_adj(m,
+					(uint16_t)(m->l2_len + m->l3_len));
 				rte_pktmbuf_chain(fp->frags[i].mb, m);
 
 				/* this mbuf should not be accessed directly */
@@ -135,12 +138,13 @@ ipv6_frag_reassemble(struct ip_frag_pkt *fp)
 #define FRAG_OFFSET(x) (rte_cpu_to_be_16(x) >> 3)
 struct rte_mbuf *
 rte_ipv6_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
-		struct rte_ip_frag_death_row *dr, struct rte_mbuf *mb, uint64_t tms,
-		struct ipv6_hdr *ip_hdr, struct ipv6_extension_fragment *frag_hdr)
+	struct rte_ip_frag_death_row *dr, struct rte_mbuf *mb, uint64_t tms,
+	struct ipv6_hdr *ip_hdr, struct ipv6_extension_fragment *frag_hdr)
 {
 	struct ip_frag_pkt *fp;
 	struct ip_frag_key key;
-	uint16_t ip_len, ip_ofs;
+	uint16_t ip_ofs;
+	int32_t ip_len;
 
 	rte_memcpy(&key.src_dst[0], ip_hdr->src_addr, 16);
 	rte_memcpy(&key.src_dst[2], ip_hdr->dst_addr, 16);
@@ -151,15 +155,17 @@ rte_ipv6_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
 	ip_ofs = FRAG_OFFSET(frag_hdr->frag_data) * 8;
 
 	/*
-	 * as per RFC2460, payload length contains all extension headers as well.
-	 * since we don't support anything but frag headers, this is what we remove
-	 * from the payload len.
+	 * as per RFC2460, payload length contains all extension headers
+	 * as well.
+	 * since we don't support anything but frag headers,
+	 * this is what we remove from the payload len.
 	 */
 	ip_len = rte_be_to_cpu_16(ip_hdr->payload_len) - sizeof(*frag_hdr);
 
 	IP_FRAG_LOG(DEBUG, "%s:%d:\n"
 		"mbuf: %p, tms: %" PRIu64
-		", key: <" IPv6_KEY_BYTES_FMT ", %#x>, ofs: %u, len: %u, flags: %#x\n"
+		", key: <" IPv6_KEY_BYTES_FMT ", %#x>, "
+		"ofs: %u, len: %d, flags: %#x\n"
 		"tbl: %p, max_cycles: %" PRIu64 ", entry_mask: %#x, "
 		"max_entries: %u, use_entries: %u\n\n",
 		__func__, __LINE__,
@@ -168,6 +174,12 @@ rte_ipv6_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
 		tbl, tbl->max_cycles, tbl->entry_mask, tbl->max_entries,
 		tbl->use_entries);
 
+	/* check that fragment length is greater then zero. */
+	if (ip_len <= 0) {
+		IP_FRAG_MBUF2DR(dr, mb);
+		return NULL;
+	}
+
 	/* try to find/add entry into the fragment's table. */
 	fp = ip_frag_find(tbl, dr, &key, tms);
 	if (fp == NULL) {
-- 
2.17.1