[dpdk-stable] [PATCH 1/2] net: fix underflow for checksum of invalid IPv4 packets

[dpdk-stable] [PATCH 1/2] net: fix underflow for checksum of invalid IPv4 packets

[Bruce Richardson]

If we receive a packet with an invalid IP header, where the total packet
length is reported as less than the IP header length, we would end up
getting an underflow in the length subtraction. This could cause us to
checksum e.g. 4GB of data in the case where the result of the subtraction
was -1. We fix this by having the function return 0 - an invalid sum - when
the length is less than the header length.

CC: stable@dpdk.org
Fixes: af75078fece3 ("first public release")
Fixes: 6006818cfb26 ("net: new checksum functions")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 lib/librte_net/rte_ip.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/lib/librte_net/rte_ip.h b/lib/librte_net/rte_ip.h
index f2a8904a2..f9b909090 100644
--- a/lib/librte_net/rte_ip.h
+++ b/lib/librte_net/rte_ip.h
@@ -310,16 +310,20 @@ rte_ipv4_phdr_cksum(const struct ipv4_hdr *ipv4_hdr, uint64_t ol_flags)
  * @param l4_hdr
  *   The pointer to the beginning of the L4 header.
  * @return
- *   The complemented checksum to set in the IP packet.
+ *   The complemented checksum to set in the IP packet
+ *   or 0 on error
  */
 static inline uint16_t
 rte_ipv4_udptcp_cksum(const struct ipv4_hdr *ipv4_hdr, const void *l4_hdr)
 {
 	uint32_t cksum;
-	uint32_t l4_len;
+	uint32_t l3_len, l4_len;
+
+	l3_len = rte_be_to_cpu_16(ipv4_hdr->total_length);
+	if (l3_len < sizeof(struct ipv4_hdr))
+		return 0;
 
-	l4_len = (uint32_t)(rte_be_to_cpu_16(ipv4_hdr->total_length) -
-		sizeof(struct ipv4_hdr));
+	l4_len = l3_len - sizeof(struct ipv4_hdr);
 
 	cksum = rte_raw_cksum(l4_hdr, l4_len);
 	cksum += rte_ipv4_phdr_cksum(ipv4_hdr, 0);
-- 
2.19.2

Re: [dpdk-stable] [dpdk-dev] [PATCH 1/2] net: fix underflow for checksum of invalid IPv4 packets

[Hemant Agrawal]

Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com<mailto:hemant.agrawal@nxp.com>>

Re: [dpdk-stable] [dpdk-dev] [PATCH 1/2] net: fix underflow for checksum of invalid IPv4 packets

[Hemant Agrawal]

After fixing my mail client issues.

Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com><mailto:hemant.agrawal@nxp.com>


On 18-Dec-18 6:45 PM, Hemant Agrawal wrote:

Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com<mailto:hemant.agrawal@nxp.com><mailto:hemant.agrawal@nxp.com><mailto:hemant.agrawal@nxp.com>>

[dpdk-stable] [PATCH 2/2] net/tap: add buffer overflow checks before checksum

[Bruce Richardson]

The checksum calculation APIs take only the packet headers pointers as
parameters, so they assume that the lengths reported in those headers are
correct. However, a malicious packet could claim to be far larger than it
is, so we need to check the header lengths in the driver before calling
the checksum API.

A better fix would be to allow the lengths to be passed into the API
function, but that would be an API break, so fixing in TAP driver for
now.

CC: stable@dpdk.org
Fixes: 8ae3023387e9 ("net/tap: add Rx/Tx checksum offload support")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 drivers/net/tap/rte_eth_tap.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 49afd38dd..0ec030bef 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -281,13 +281,27 @@ tap_verify_csum(struct rte_mbuf *mbuf)
 		l3_len = 4 * (iph->version_ihl & 0xf);
 		if (unlikely(l2_len + l3_len > rte_pktmbuf_data_len(mbuf)))
 			return;
+		/* check that the total length reported by header is not
+		 * greater than the total received size
+		 */
+		if (l2_len + rte_be_to_cpu_16(iph->total_length) >
+				rte_pktmbuf_data_len(mbuf))
+			return;
 
 		cksum = ~rte_raw_cksum(iph, l3_len);
 		mbuf->ol_flags |= cksum ?
 			PKT_RX_IP_CKSUM_BAD :
 			PKT_RX_IP_CKSUM_GOOD;
 	} else if (l3 == RTE_PTYPE_L3_IPV6) {
+		struct ipv6_hdr *iph = l3_hdr;
+
 		l3_len = sizeof(struct ipv6_hdr);
+		/* check that the total length reported by header is not
+		 * greater than the total received size
+		 */
+		if (l2_len + l3_len + rte_be_to_cpu_16(iph->payload_len) >
+				rte_pktmbuf_data_len(mbuf))
+			return;
 	} else {
 		/* IPv6 extensions are not supported */
 		return;
-- 
2.19.2

Re: [dpdk-stable] [dpdk-dev] [PATCH 2/2] net/tap: add buffer overflow checks before checksum

[Ferruh Yigit]

On 12/17/2018 3:50 PM, Bruce Richardson wrote:
> The checksum calculation APIs take only the packet headers pointers as
> parameters, so they assume that the lengths reported in those headers are
> correct. However, a malicious packet could claim to be far larger than it
> is, so we need to check the header lengths in the driver before calling
> the checksum API.
> 
> A better fix would be to allow the lengths to be passed into the API
> function, but that would be an API break, so fixing in TAP driver for
> now.
> 
> CC: stable@dpdk.org
> Fixes: 8ae3023387e9 ("net/tap: add Rx/Tx checksum offload support")
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

Re: [dpdk-stable] [PATCH 2/2] net/tap: add buffer overflow checks before checksum

[Wiles, Keith]

> On Dec 17, 2018, at 9:50 AM, Richardson, Bruce <bruce.richardson@intel.com> wrote:
> 
> The checksum calculation APIs take only the packet headers pointers as
> parameters, so they assume that the lengths reported in those headers are
> correct. However, a malicious packet could claim to be far larger than it
> is, so we need to check the header lengths in the driver before calling
> the checksum API.
> 
> A better fix would be to allow the lengths to be passed into the API
> function, but that would be an API break, so fixing in TAP driver for
> now.
> 
> CC: stable@dpdk.org
> Fixes: 8ae3023387e9 ("net/tap: add Rx/Tx checksum offload support")
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> —

Acked-by: Keith Wiles <keith.wiles@intel.com>

Regards,
Keith