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netlink: add nested array policy validation

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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 <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Johannes Berg 2018-09-26 11:15:34 +02:00 • committed by David S. Miller
commit 1501d13596
2 changed files with 62 additions and 1 deletions
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51
lib/nlattr.c
View file

@ -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;