netlink: make validation more configurable for future strictness

We currently have two levels of strict validation:

 1) liberal (default)
     - undefined (type >= max) & NLA_UNSPEC attributes accepted
     - attribute length >= expected accepted
     - garbage at end of message accepted
 2) strict (opt-in)
     - NLA_UNSPEC attributes accepted
     - attribute length >= expected accepted

Split out parsing strictness into four different options:
 * TRAILING     - check that there's no trailing data after parsing
                  attributes (in message or nested)
 * MAXTYPE      - reject attrs > max known type
 * UNSPEC       - reject attributes with NLA_UNSPEC policy entries
 * STRICT_ATTRS - strictly validate attribute size

The default for future things should be *everything*.
The current *_strict() is a combination of TRAILING and MAXTYPE,
and is renamed to _deprecated_strict().
The current regular parsing has none of this, and is renamed to
*_parse_deprecated().

Additionally it allows us to selectively set one of the new flags
even on old policies. Notably, the UNSPEC flag could be useful in
this case, since it can be arranged (by filling in the policy) to
not be an incompatible userspace ABI change, but would then going
forward prevent forgetting attribute entries. Similar can apply
to the POLICY flag.

We end up with the following renames:
 * nla_parse           -> nla_parse_deprecated
 * nla_parse_strict    -> nla_parse_deprecated_strict
 * nlmsg_parse         -> nlmsg_parse_deprecated
 * nlmsg_parse_strict  -> nlmsg_parse_deprecated_strict
 * nla_parse_nested    -> nla_parse_nested_deprecated
 * nla_validate_nested -> nla_validate_nested_deprecated

Using spatch, of course:
    @@
    expression TB, MAX, HEAD, LEN, POL, EXT;
    @@
    -nla_parse(TB, MAX, HEAD, LEN, POL, EXT)
    +nla_parse_deprecated(TB, MAX, HEAD, LEN, POL, EXT)

    @@
    expression NLH, HDRLEN, TB, MAX, POL, EXT;
    @@
    -nlmsg_parse(NLH, HDRLEN, TB, MAX, POL, EXT)
    +nlmsg_parse_deprecated(NLH, HDRLEN, TB, MAX, POL, EXT)

    @@
    expression NLH, HDRLEN, TB, MAX, POL, EXT;
    @@
    -nlmsg_parse_strict(NLH, HDRLEN, TB, MAX, POL, EXT)
    +nlmsg_parse_deprecated_strict(NLH, HDRLEN, TB, MAX, POL, EXT)

    @@
    expression TB, MAX, NLA, POL, EXT;
    @@
    -nla_parse_nested(TB, MAX, NLA, POL, EXT)
    +nla_parse_nested_deprecated(TB, MAX, NLA, POL, EXT)

    @@
    expression START, MAX, POL, EXT;
    @@
    -nla_validate_nested(START, MAX, POL, EXT)
    +nla_validate_nested_deprecated(START, MAX, POL, EXT)

    @@
    expression NLH, HDRLEN, MAX, POL, EXT;
    @@
    -nlmsg_validate(NLH, HDRLEN, MAX, POL, EXT)
    +nlmsg_validate_deprecated(NLH, HDRLEN, MAX, POL, EXT)

For this patch, don't actually add the strict, non-renamed versions
yet so that it breaks compile if I get it wrong.

Also, while at it, make nla_validate and nla_parse go down to a
common __nla_validate_parse() function to avoid code duplication.

Ultimately, this allows us to have very strict validation for every
new caller of nla_parse()/nlmsg_parse() etc as re-introduced in the
next patch, while existing things will continue to work as is.

In effect then, this adds fully strict validation for any new command.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 12 insertions, 11 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 356677c3a0c2..3b99fc3de9ac 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1375,8 +1375,8 @@ static int ovs_flow_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
 	u32 ufid_flags;
 	int err;
 
-	err = genlmsg_parse(cb->nlh, &dp_flow_genl_family, a,
-			    OVS_FLOW_ATTR_MAX, flow_policy, NULL);
+	err = genlmsg_parse_deprecated(cb->nlh, &dp_flow_genl_family, a,
+				       OVS_FLOW_ATTR_MAX, flow_policy, NULL);
 	if (err)
 		return err;
 	ufid_flags = ovs_nla_get_ufid_flags(a[OVS_FLOW_ATTR_UFID_FLAGS]);
diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 2427b672107a..54eb80dd2dc6 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -2854,8 +2854,8 @@ static int validate_userspace(const struct nlattr *attr)
 	struct nlattr *a[OVS_USERSPACE_ATTR_MAX + 1];
 	int error;
 
-	error = nla_parse_nested(a, OVS_USERSPACE_ATTR_MAX, attr,
-				 userspace_policy, NULL);
+	error = nla_parse_nested_deprecated(a, OVS_USERSPACE_ATTR_MAX, attr,
+					    userspace_policy, NULL);
 	if (error)
 		return error;
 
@@ -2885,8 +2885,9 @@ static int validate_and_copy_check_pkt_len(struct net *net,
 	int nested_acts_start;
 	int start, err;
 
-	err = nla_parse_strict(a, OVS_CHECK_PKT_LEN_ATTR_MAX, nla_data(attr),
-			       nla_len(attr), cpl_policy, NULL);
+	err = nla_parse_deprecated_strict(a, OVS_CHECK_PKT_LEN_ATTR_MAX,
+					  nla_data(attr), nla_len(attr),
+					  cpl_policy, NULL);
 	if (err)
 		return err;
 
diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
index fdc8be7fd8f3..9c89e8539a5a 100644
--- a/net/openvswitch/meter.c
+++ b/net/openvswitch/meter.c
@@ -227,9 +227,9 @@ static struct dp_meter *dp_meter_create(struct nlattr **a)
 		struct nlattr *attr[OVS_BAND_ATTR_MAX + 1];
 		u32 band_max_delta_t;
 
-		err = nla_parse((struct nlattr **)&attr, OVS_BAND_ATTR_MAX,
-				nla_data(nla), nla_len(nla), band_policy,
-				NULL);
+		err = nla_parse_deprecated((struct nlattr **)&attr,
+					   OVS_BAND_ATTR_MAX, nla_data(nla),
+					   nla_len(nla), band_policy, NULL);
 		if (err)
 			goto exit_free_meter;
 
diff --git a/net/openvswitch/vport-vxlan.c b/net/openvswitch/vport-vxlan.c
index 54965ff8cc66..f3c54871f9e1 100644
--- a/net/openvswitch/vport-vxlan.c
+++ b/net/openvswitch/vport-vxlan.c
@@ -70,8 +70,8 @@ static int vxlan_configure_exts(struct vport *vport, struct nlattr *attr,
 	if (nla_len(attr) < sizeof(struct nlattr))
 		return -EINVAL;
 
-	err = nla_parse_nested(exts, OVS_VXLAN_EXT_MAX, attr, exts_policy,
-			       NULL);
+	err = nla_parse_nested_deprecated(exts, OVS_VXLAN_EXT_MAX, attr,
+					  exts_policy, NULL);
 	if (err < 0)
 		return err;