From 1501d13596b92d6d1f0ea5e104be838188b6e026 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 26 Sep 2018 11:15:34 +0200 Subject: netlink: add nested array policy validation 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 Signed-off-by: David S. Miller --- lib/nlattr.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) (limited to 'lib/nlattr.c') diff --git a/lib/nlattr.c b/lib/nlattr.c index 04750f88477c..2f8feff669a7 100644 --- a/lib/nlattr.c +++ b/lib/nlattr.c @@ -67,6 +67,34 @@ static int validate_nla_bitfield32(const struct nlattr *nla, return 0; } +static int nla_validate_array(const struct nlattr *head, int len, int maxtype, + const struct nla_policy *policy, + struct netlink_ext_ack *extack) +{ + 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(nla_data(entry), nla_len(entry), + maxtype, policy, extack); + 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) @@ -169,6 +197,29 @@ static int validate_nla(const struct nlattr *nla, int maxtype, } } 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) + goto out_err; + if (pt->validation_data) { + int err; + + err = nla_validate_array(nla_data(nla), nla_len(nla), + pt->len, pt->validation_data, + extack); + if (err < 0) { + /* + * return directly to preserve the inner + * error message/attribute pointer + */ + return err; + } + } + break; default: if (pt->len) minlen = pt->len; -- cgit v1.2.3