From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: [PATCH v2 5/5] netlink: add nested array policy validation Date: Wed, 19 Sep 2018 21:49:05 +0200 Message-ID: <20180919194905.16462-6-johannes@sipsolutions.net> References: <20180919194905.16462-1-johannes@sipsolutions.net> Cc: David Ahern , Johannes Berg To: linux-wireless@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from s3.sipsolutions.net ([144.76.43.62]:59470 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732824AbeITB2s (ORCPT ); Wed, 19 Sep 2018 21:28:48 -0400 In-Reply-To: <20180919194905.16462-1-johannes@sipsolutions.net> Sender: netdev-owner@vger.kernel.org List-ID: From: Johannes Berg 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 --- include/net/netlink.h | 12 +++++++++++- lib/nlattr.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 62 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 4cbfc64f6d10..9d8e1dc71680 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) @@ -166,6 +194,29 @@ 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; -- 2.14.4