From: Johannes Berg <johannes.berg@xxxxxxxxx>
Sometimes nested netlink attributes are just used as arrays, with
the nla_type() of each not being used; we have this in nl80211 and
e.g. NFTA_SET_ELEM_LIST_ELEMENTS.
Add the ability to validate this type of message directly in the
policy, by adding the type NLA_NESTED_ARRAY which does exactly
this: require a first level of nesting but ignore the attribute
type, and then inside each require a second level of nested and
validate those attributes against a given policy (if present).
Note that some nested array types actually require that all of
the entries have the same index, this is possible to express in
a nested policy already, apart from the validation that only the
one allowed type is used.
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
include/net/netlink.h | 12 +++++++++++-
lib/nlattr.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 58 insertions(+), 1 deletion(-)
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 91907852da1c..3698ca8ff92c 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -172,6 +172,7 @@ enum {
NLA_FLAG,
NLA_MSECS,
NLA_NESTED,
+ NLA_NESTED_ARRAY,
NLA_NUL_STRING,
NLA_BINARY,
NLA_S8,
@@ -200,7 +201,8 @@ enum {
* NLA_NUL_STRING Maximum length of string (excluding NUL)
* NLA_FLAG Unused
* NLA_BINARY Maximum length of attribute payload
- * NLA_NESTED Length verification is done by checking len of
+ * NLA_NESTED,
+ * NLA_NESTED_ARRAY Length verification is done by checking len of
* nested header (or empty); len field is used if
* validation_data is also used, for the max attr
* number in the nested policy.
@@ -230,6 +232,12 @@ enum {
* `len' to the max attribute number.
* Note that nla_parse() will validate, but of course not
* parse, the nested sub-policies.
+ * NLA_NESTED_ARRAY Points to a nested policy to validate, must also set
+ * `len' to the max attribute number. The difference to
+ * NLA_NESTED is the structure - NLA_NESTED has the
+ * nested attributes directly inside, while an array has
+ * the nested attributes at another level down and the
+ * attributes directly in the nesting don't matter.
* All other Unused
*
* Example:
@@ -255,6 +263,8 @@ struct nla_policy {
#define NLA_POLICY_NESTED(maxattr, policy) \
{ .type = NLA_NESTED, .validation_data = policy, .len = maxattr }
+#define NLA_POLICY_NESTED_ARRAY(maxattr, policy) \
+ { .type = NLA_NESTED_ARRAY, .validation_data = policy, .len = maxattr }
/**
* struct nl_info - netlink source information
diff --git a/lib/nlattr.c b/lib/nlattr.c
index c0ea8a78eda6..234763b41ab7 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -72,6 +72,35 @@ static int nla_validate_parse(const struct nlattr *head, int len, int maxtype,
struct netlink_ext_ack *extack, bool *extack_set,
struct nlattr **tb);
+static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
+ const struct nla_policy *policy,
+ struct netlink_ext_ack *extack, bool *extack_set)
+{
+ const struct nlattr *entry;
+ int rem;
+
+ nla_for_each_attr(entry, head, len, rem) {
+ int ret;
+
+ if (nla_len(entry) == 0)
+ continue;
+
+ if (nla_len(entry) < NLA_HDRLEN) {
+ NL_SET_ERR_MSG_ATTR(extack, entry,
+ "Array element too short");
+ return -ERANGE;
+ }
+
+ ret = nla_validate_parse(nla_data(entry), nla_len(entry),
+ maxtype, policy, extack, extack_set,
+ NULL);
+ if (ret < 0)
+ return ret;
+ }
+
+ return 0;
+}
+
static int validate_nla(const struct nlattr *nla, int maxtype,
const struct nla_policy *policy,
struct netlink_ext_ack *extack, bool *extack_set)
@@ -165,6 +194,24 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
return err;
}
break;
+ case NLA_NESTED_ARRAY:
+ /* a nested array attribute is allowed to be empty; if its not,
+ * it must have a size of at least NLA_HDRLEN.
+ */
+ if (attrlen == 0)
+ break;
+ if (attrlen < NLA_HDRLEN)
+ return -ERANGE;
+ if (pt->validation_data) {
+ int err;
+
+ err = nla_validate_array(nla_data(nla), nla_len(nla),
+ pt->len, pt->validation_data,
+ extack, extack_set);
+ if (err < 0)
+ return err;
+ }
+ break;
default:
if (pt->len)
minlen = pt->len;
--
2.14.4
