[PATCH v2 4/5] netlink: allow NLA_NESTED to specify nested policy to validate
From: Johannes Berg <johannes@sipsolutions.net>
Date: 2018-09-20 01:28:48
Also in:
linux-wireless
Subsystem:
library code, networking [general], the rest · Maintainers:
Andrew Morton, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Johannes Berg <redacted> Now that we have a validation_data pointer, and the len field in the policy is unused for NLA_NESTED, we can allow using them both to have nested validation. This can be nice in code, although we still have to use nla_parse_nested() or similar which would also take a policy; however, it also serves as documentation in the policy without requiring a look at the code. Signed-off-by: Johannes Berg <redacted> --- include/net/netlink.h | 13 +++++++++++-- lib/nlattr.c | 14 ++++++++++++++ 2 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 0d698215d4d9..91907852da1c 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h@@ -200,8 +200,10 @@ enum { * NLA_NUL_STRING Maximum length of string (excluding NUL) * NLA_FLAG Unused * NLA_BINARY Maximum length of attribute payload - * NLA_NESTED Don't use `len' field -- length verification is - * done by checking len of nested header (or empty) + * NLA_NESTED 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. * NLA_U8, NLA_U16, * NLA_U32, NLA_U64, * NLA_S8, NLA_S16,
@@ -224,6 +226,10 @@ enum { * NLA_REJECT This attribute is always rejected and validation data * may point to a string to report as the error instead * of the generic one in extended ACK. + * NLA_NESTED Points to a nested policy to validate, must also set + * `len' to the max attribute number. + * Note that nla_parse() will validate, but of course not + * parse, the nested sub-policies. * All other Unused * * Example:
@@ -247,6 +253,9 @@ struct nla_policy { #define NLA_POLICY_ETH_ADDR NLA_POLICY_EXACT_LEN(ETH_ALEN) #define NLA_POLICY_ETH_ADDR_COMPAT NLA_POLICY_EXACT_LEN_WARN(ETH_ALEN) +#define NLA_POLICY_NESTED(maxattr, policy) \ + { .type = NLA_NESTED, .validation_data = policy, .len = maxattr } + /** * struct nl_info - netlink source information * @nlh: Netlink message header of original request
diff --git a/lib/nlattr.c b/lib/nlattr.c
index ff6d48d7c19a..4cbfc64f6d10 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c@@ -152,6 +152,20 @@ static int validate_nla(const struct nlattr *nla, int maxtype, */ if (attrlen == 0) break; + if (attrlen < NLA_HDRLEN) + goto out_err; + if (pt->validation_data) { + err = nla_validate(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