net: sched: ensure opts_len <= IP_TUNNEL_OPTS_MAX in act_tunnel_key

This change “net: sched: ensure opts_len ⇐ IP_TUNNEL_OPTS_MAX in act_tunnel_key” (commit 4f0e97d) in Linux kernel is authored by Xin Long <lucien.xin [at] gmail.com> on Mon Nov 18 17:39:34 2019 +0800.

Description of "net: sched: ensure opts_len <= IP_TUNNEL_OPTS_MAX in act_tunnel_key"

The change “net: sched: ensure opts_len ⇐ IP_TUNNEL_OPTS_MAX in act_tunnel_key” introduces changes as follows.

net: sched: ensure opts_len <= IP_TUNNEL_OPTS_MAX in act_tunnel_key

info->options_len is 'u8' type, and when opts_len with a value >
IP_TUNNEL_OPTS_MAX, 'info->options_len = opts_len' will cast int
to u8 and set a wrong value to info->options_len.

Kernel crashed in my test when doing:

  # opts="0102:80:00800022"
  # for i in {1..99}; do opts="$opts,0102:80:00800022"; done
  # ip link add name geneve0 type geneve dstport 0 external
  # tc qdisc add dev eth0 ingress
  # tc filter add dev eth0 protocol ip parent ffff: \
       flower indev eth0 ip_proto udp action tunnel_key \
       set src_ip 10.0.99.192 dst_ip 10.0.99.193 \
       dst_port 6081 id 11 geneve_opts $opts \
       action mirred egress redirect dev geneve0

So we should do the similar check as cls_flower does, return error
when opts_len > IP_TUNNEL_OPTS_MAX in tunnel_key_copy_opts().

Fixes: 0ed5269f9e41 ("net/sched: add tunnel option support to act_tunnel_key")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Linux kernel releases containing commit 4f0e97d

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "net: sched: ensure opts_len <= IP_TUNNEL_OPTS_MAX in act_tunnel_key"

There are 4 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/sched/act_tunnel_key.c | 4 ++++
 1 file changed, 4 insertions(+)
 
diff --git a/net/sched/act_tunnel_key.c b/net/sched/act_tunnel_key.c
index 2f83a79f76aa..d55669e14741 100644
--- a/net/sched/act_tunnel_key.c
+++ b/net/sched/act_tunnel_key.c
@@ -135,6 +135,10 @@ static int tunnel_key_copy_opts(const struct nlattr *nla, u8 *dst,
 			if (opt_len < 0)
 				return opt_len;
 			opts_len += opt_len;
+			if (opts_len > IP_TUNNEL_OPTS_MAX) {
+				NL_SET_ERR_MSG(extack, "Tunnel options exceeds max size");
+				return -EINVAL;
+			}
 			if (dst) {
 				dst_len -= opt_len;
 				dst += opt_len;

The commit for this change in Linux stable tree is 4f0e97d (patch).

Last modified: 2020/02/08