Introduce a helper for icmp type checking - icmp_is_valid_type.
There is a number of code paths handling ICMP packets. To check
icmp type validity, some of those code paths perform the check
`type <= NR_ICMP_TYPES`. Since the introduction of ICMP_EXT_ECHO
and ICMP_EXT_ECHOREPLY (RFC 8335), this check is no longer correct.
To fix this inconsistency and avoid further problems with future
ICMP types, the patch inserts the icmp_is_valid type helper
wherever it is required. The helper checks if the type is less than
NR_ICMP_TYPES or is equal to ICMP_EXT_ECHO/REPLY.
NR_ICMP_TYPES could theoretically be increased to ICMP_EXT_ECHOREPLY
(43), but that would not make sense as types 19-41 are not used.
Signed-off-by: Mathias Lark <mathias.lark@xxxxxxxxx>
---
include/linux/icmp.h | 4 ++++
net/ipv4/icmp.c | 8 +++-----
net/netfilter/nf_conntrack_proto_icmp.c | 4 +---
3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/include/linux/icmp.h b/include/linux/icmp.h
index 0af4d210ee31..e979c80696b0 100644
--- a/include/linux/icmp.h
+++ b/include/linux/icmp.h
@@ -36,6 +36,11 @@ static inline bool icmp_is_err(int type)
return false;
}
+static inline bool icmp_is_valid_type(int type)
+{
+ return type <= NR_ICMP_TYPES || type == ICMP_EXT_ECHO || type == ICMP_EXT_ECHOREPLY;
+}
+
void ip_icmp_error_rfc4884(const struct sk_buff *skb,
struct sock_ee_data_rfc4884 *out,
int thlen, int off);
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 236debd9fded..686f3133370f 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -273,7 +273,7 @@ EXPORT_SYMBOL(icmp_global_allow);
static bool icmpv4_mask_allow(struct net *net, int type, int code)
{
- if (type > NR_ICMP_TYPES)
+ if (!icmp_is_valid_type(type))
return true;
/* Don't limit PMTU discovery. */
@@ -661,7 +661,7 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
* Assume any unknown ICMP type is an error. This
* isn't specified by the RFC, but think about it..
*/
- if (*itp > NR_ICMP_TYPES ||
+ if (!icmp_is_valid_type(*itp) ||
icmp_pointers[*itp].error)
goto out;
}
@@ -1225,12 +1225,10 @@ int icmp_rcv(struct sk_buff *skb)
}
/*
- * 18 is the highest 'known' ICMP type. Anything else is a mystery
- *
* RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
* discarded.
*/
- if (icmph->type > NR_ICMP_TYPES) {
+ if (!icmp_is_valid_type(icmph->type)) {
reason = SKB_DROP_REASON_UNHANDLED_PROTO;
goto error;
}
diff --git a/net/netfilter/nf_conntrack_proto_icmp.c b/net/netfilter/nf_conntrack_proto_icmp.c
index b38b7164acd5..ba4462c393be 100644
--- a/net/netfilter/nf_conntrack_proto_icmp.c
+++ b/net/netfilter/nf_conntrack_proto_icmp.c
@@ -225,12 +225,10 @@ int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
}
/*
- * 18 is the highest 'known' ICMP type. Anything else is a mystery
- *
* RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
* discarded.
*/
- if (icmph->type > NR_ICMP_TYPES) {
+ if (!icmp_is_valid_type(icmph->type)) {
icmp_error_log(skb, state, "invalid icmp type");
return -NF_ACCEPT;
}
--
2.36.1
