icmp: fix icmp_ext_echo_iio parsing in icmp_build_probe

In icmp_build_probe(), the icmp_ext_echo_iio parsing should be done
step by step and skb_header_pointer() return value should always be
checked, this patch fixes 3 places in there:

  - On case ICMP_EXT_ECHO_CTYPE_NAME, it should only copy ident.name
    from skb by skb_header_pointer(), its len is ident_len. Besides,
    the return value of skb_header_pointer() should always be checked.

  - On case ICMP_EXT_ECHO_CTYPE_INDEX, move ident_len check ahead of
    skb_header_pointer(), and also do the return value check for
    skb_header_pointer().

  - On case ICMP_EXT_ECHO_CTYPE_ADDR, before accessing iio->ident.addr.
    ctype3_hdr.addrlen, skb_header_pointer() should be called first,
    then check its return value and ident_len.
    On subcases ICMP_AFI_IP and ICMP_AFI_IP6, also do check for ident.
    addr.ctype3_hdr.addrlen and skb_header_pointer()'s return value.
    On subcase ICMP_AFI_IP, the len for skb_header_pointer() should be
    "sizeof(iio->extobj_hdr) + sizeof(iio->ident.addr.ctype3_hdr) +
    sizeof(struct in_addr)" or "ident_len".

v1->v2:
  - To make it more clear, call skb_header_pointer() once only for
    iio->indent's parsing as Jakub Suggested.
v2->v3:
  - The extobj_hdr.length check against sizeof(_iio) should be done
    before calling skb_header_pointer(), as Eric noticed.

Fixes: d329ea5bd884 ("icmp: add response to RFC 8335 PROBE messages")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/31628dd76657ea62f5cf78bb55da6b35240831f1.1634205050.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 8b30cad..b7e277d 100644 (file)
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -1054,14 +1054,19 @@ bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
        iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
        if (!ext_hdr || !iio)
                goto send_mal_query;
-       if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr))
+       if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
+           ntohs(iio->extobj_hdr.length) > sizeof(_iio))
                goto send_mal_query;
        ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
+       iio = skb_header_pointer(skb, sizeof(_ext_hdr),
+                                sizeof(iio->extobj_hdr) + ident_len, &_iio);
+       if (!iio)
+               goto send_mal_query;
+
        status = 0;
        dev = NULL;
        switch (iio->extobj_hdr.class_type) {
        case ICMP_EXT_ECHO_CTYPE_NAME:
-               iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(_iio), &_iio);
                if (ident_len >= IFNAMSIZ)
                        goto send_mal_query;
                memset(buff, 0, sizeof(buff));
@@ -1069,30 +1074,24 @@ bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
                dev = dev_get_by_name(net, buff);
                break;
        case ICMP_EXT_ECHO_CTYPE_INDEX:
-               iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr) +
-                                        sizeof(iio->ident.ifindex), &_iio);
                if (ident_len != sizeof(iio->ident.ifindex))
                        goto send_mal_query;
                dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
                break;
        case ICMP_EXT_ECHO_CTYPE_ADDR:
-               if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
+               if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
+                   ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
                                 iio->ident.addr.ctype3_hdr.addrlen)
                        goto send_mal_query;
                switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
                case ICMP_AFI_IP:
-                       iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr) +
-                                                sizeof(struct in_addr), &_iio);
-                       if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
-                                        sizeof(struct in_addr))
+                       if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
                                goto send_mal_query;
                        dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
                        break;
 #if IS_ENABLED(CONFIG_IPV6)
                case ICMP_AFI_IP6:
-                       iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(_iio), &_iio);
-                       if (ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
-                                        sizeof(struct in6_addr))
+                       if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
                                goto send_mal_query;
                        dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
                        dev_hold(dev);