[PATCH net-next v2 2/4] bridge: simplify ip_mc_check_igmp() and ipv6_mc_check_mld() internals

Linus Lüssing
2019-01-21T07:22:37Z

With this patch the internal use of the skb_trimmed is reduced to
the ICMPv6/IGMP checksum verification. And for the length checks
the newly introduced helper functions are used instead of calculating
and checking with skb->len directly.

These changes should hopefully make it easier to verify that length
checks are performed properly.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
net/ipv4/igmp.c | 51 ++++++++++++++++++-----------------------
net/ipv6/mcast_snoop.c | 62 ++++++++++++++++++++++++--------------------------
2 files changed, 52 insertions(+), 61 deletions(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index b1f6d93282d7..a40e48ded10d 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1493,22 +1493,22 @@ static int ip_mc_check_igmp_reportv3(struct sk_buff *skb)

len += sizeof(struct igmpv3_report);

- return pskb_may_pull(skb, len) ? 0 : -EINVAL;
+ return ip_mc_may_pull(skb, len) ? 0 : -EINVAL;
}

static int ip_mc_check_igmp_query(struct sk_buff *skb)
{
- unsigned int len = skb_transport_offset(skb);
-
- len += sizeof(struct igmphdr);
- if (skb->len < len)
- return -EINVAL;
+ unsigned int transport_len = ip_transport_len(skb);
+ unsigned int len;

/* IGMPv{1,2}? */
- if (skb->len != len) {
+ if (transport_len != sizeof(struct igmphdr)) {
/* or IGMPv3? */
- len += sizeof(struct igmpv3_query) - sizeof(struct igmphdr);
- if (skb->len < len || !pskb_may_pull(skb, len))
+ if (transport_len < sizeof(struct igmpv3_query))
+ return -EINVAL;
+
+ len = skb_transport_offset(skb) + sizeof(struct igmpv3_query);
+ if (!ip_mc_may_pull(skb, len))
return -EINVAL;
}

@@ -1544,35 +1544,24 @@ static inline __sum16 ip_mc_validate_checksum(struct sk_buff *skb)
return skb_checksum_simple_validate(skb);
}

-static int __ip_mc_check_igmp(struct sk_buff *skb)
-
+static int ip_mc_check_igmp_csum(struct sk_buff *skb)
{
- struct sk_buff *skb_chk;
- unsigned int transport_len;
unsigned int len = skb_transport_offset(skb) + sizeof(struct igmphdr);
- int ret = -EINVAL;
+ unsigned int transport_len = ip_transport_len(skb);
+ struct sk_buff *skb_chk;

- transport_len = ntohs(ip_hdr(skb)->tot_len) - ip_hdrlen(skb);
+ if (!ip_mc_may_pull(skb, len))
+ return -EINVAL;

skb_chk = skb_checksum_trimmed(skb, transport_len,
ip_mc_validate_checksum);
if (!skb_chk)
- goto err;
+ return -EINVAL;

- if (!pskb_may_pull(skb_chk, len))
- goto err;
-
- ret = ip_mc_check_igmp_msg(skb_chk);
- if (ret)
- goto err;
-
- ret = 0;
-
-err:
- if (skb_chk && skb_chk != skb)
+ if (skb_chk != skb)
kfree_skb(skb_chk);

- return ret;
+ return 0;
}

/**
@@ -1600,7 +1589,11 @@ int ip_mc_check_igmp(struct sk_buff *skb)
if (ip_hdr(skb)->protocol != IPPROTO_IGMP)
return -ENOMSG;

- return __ip_mc_check_igmp(skb);
+ ret = ip_mc_check_igmp_csum(skb);
+ if (ret < 0)
+ return ret;
+
+ return ip_mc_check_igmp_msg(skb);
}
EXPORT_SYMBOL(ip_mc_check_igmp);

diff --git a/net/ipv6/mcast_snoop.c b/net/ipv6/mcast_snoop.c
index 1a917dc80d5e..a72ddfc40eb3 100644
--- a/net/ipv6/mcast_snoop.c
+++ b/net/ipv6/mcast_snoop.c
@@ -77,27 +77,27 @@ static int ipv6_mc_check_mld_reportv2(struct sk_buff *skb)

len += sizeof(struct mld2_report);

- return pskb_may_pull(skb, len) ? 0 : -EINVAL;
+ return ipv6_mc_may_pull(skb, len) ? 0 : -EINVAL;
}

static int ipv6_mc_check_mld_query(struct sk_buff *skb)
{
+ unsigned int transport_len = ipv6_transport_len(skb);
struct mld_msg *mld;
- unsigned int len = skb_transport_offset(skb);
+ unsigned int len;

/* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
if (!(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL))
return -EINVAL;

- len += sizeof(struct mld_msg);
- if (skb->len < len)
- return -EINVAL;
-
/* MLDv1? */
- if (skb->len != len) {
+ if (transport_len != sizeof(struct mld_msg)) {
/* or MLDv2? */
- len += sizeof(struct mld2_query) - sizeof(struct mld_msg);
- if (skb->len < len || !pskb_may_pull(skb, len))
+ if (transport_len < sizeof(struct mld2_query))
+ return -EINVAL;
+
+ len = skb_transport_offset(skb) + sizeof(struct mld2_query);
+ if (!ipv6_mc_may_pull(skb, len))
return -EINVAL;
}

@@ -115,7 +115,13 @@ static int ipv6_mc_check_mld_query(struct sk_buff *skb)

static int ipv6_mc_check_mld_msg(struct sk_buff *skb)
{
- struct mld_msg *mld = (struct mld_msg *)skb_transport_header(skb);
+ unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg);
+ struct mld_msg *mld;
+
+ if (!ipv6_mc_may_pull(skb, len))
+ return -EINVAL;
+
+ mld = (struct mld_msg *)skb_transport_header(skb);

switch (mld->mld_type) {
case ICMPV6_MGM_REDUCTION:
@@ -136,36 +142,24 @@ static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb)
return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo);
}

-static int __ipv6_mc_check_mld(struct sk_buff *skb)
-
+static int ipv6_mc_check_icmpv6(struct sk_buff *skb)
{
- struct sk_buff *skb_chk = NULL;
- unsigned int transport_len;
- unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg);
- int ret = -EINVAL;
+ unsigned int len = skb_transport_offset(skb) + sizeof(struct icmp6hdr);
+ unsigned int transport_len = ipv6_transport_len(skb);
+ struct sk_buff *skb_chk;

- transport_len = ntohs(ipv6_hdr(skb)->payload_len);
- transport_len -= skb_transport_offset(skb) - sizeof(struct ipv6hdr);
+ if (!ipv6_mc_may_pull(skb, len))
+ return -EINVAL;

skb_chk = skb_checksum_trimmed(skb, transport_len,
ipv6_mc_validate_checksum);
if (!skb_chk)
- goto err;
+ return -EINVAL;

- if (!pskb_may_pull(skb_chk, len))
- goto err;
-
- ret = ipv6_mc_check_mld_msg(skb_chk);
- if (ret)
- goto err;
-
- ret = 0;
-
-err:
- if (skb_chk && skb_chk != skb)
+ if (skb_chk != skb)
kfree_skb(skb_chk);

- return ret;
+ return 0;
}

/**
@@ -195,6 +189,10 @@ int ipv6_mc_check_mld(struct sk_buff *skb)
if (ret < 0)
return ret;

- return __ipv6_mc_check_mld(skb);
+ ret = ipv6_mc_check_icmpv6(skb);
+ if (ret < 0)
+ return ret;
+
+ return ipv6_mc_check_mld_msg(skb);
}
EXPORT_SYMBOL(ipv6_mc_check_mld);
--
2.11.0