linux-kernel - [PATCH 4.19 006/306] net: sched: ensure opts_len <= IP_TUNNEL_OPTS_MAX in act_tunnel

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Message-Id: <20191127203115.209535927@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:27:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xin Long <lucien.xin@...il.com>,
        Simon Horman <simon.horman@...ronome.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 006/306] net: sched: ensure opts_len <= IP_TUNNEL_OPTS_MAX in act_tunnel_key

From: Xin Long <lucien.xin@...il.com>

[ Upstream commit 4f0e97d070984d487df027f163e52bb72d1713d8 ]

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@...il.com>
Reviewed-by: Simon Horman <simon.horman@...ronome.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/act_tunnel_key.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/sched/act_tunnel_key.c
+++ b/net/sched/act_tunnel_key.c
@@ -137,6 +137,10 @@ static int tunnel_key_copy_opts(const st
 			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;