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Message-Id: <20201006142714.3c8b8db03517.I6dae2c514a6abc924ee8b3e2befb0d51b086cf70@changeid>
Date: Tue, 6 Oct 2020 14:32:02 +0200
From: Johannes Berg <johannes@...solutions.net>
To: netdev@...r.kernel.org
Cc: dsahern@...il.com, Jakub Kicinski <kuba@...nel.org>,
Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 2/2] netlink: export policy in extended ACK
From: Johannes Berg <johannes.berg@...el.com>
Add a new attribute NLMSGERR_ATTR_POLICY to the extended ACK
to advertise the policy, e.g. if an attribute was out of range,
you'll know the range that's permissible.
Add new NL_SET_ERR_MSG_ATTR_POL() and NL_SET_ERR_MSG_ATTR_POL()
macros to set this, since realistically it's only useful to do
this when the bad attribute (offset) is also returned.
Use it in lib/nlattr.c which practically does all the policy
validation.
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
include/linux/netlink.h | 30 ++++++++++++++++++++----------
include/net/netlink.h | 3 +++
include/uapi/linux/netlink.h | 2 ++
lib/nlattr.c | 35 ++++++++++++++++++-----------------
net/netlink/af_netlink.c | 6 ++++++
net/netlink/policy.c | 17 +++++++++++++++++
6 files changed, 66 insertions(+), 27 deletions(-)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index e3e49f0e5c13..666cd0390699 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -68,12 +68,14 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
* @_msg: message string to report - don't access directly, use
* %NL_SET_ERR_MSG
* @bad_attr: attribute with error
+ * @policy: policy for a bad attribute
* @cookie: cookie data to return to userspace (for success)
* @cookie_len: actual cookie data length
*/
struct netlink_ext_ack {
const char *_msg;
const struct nlattr *bad_attr;
+ const struct nla_policy *policy;
u8 cookie[NETLINK_MAX_COOKIE_LEN];
u8 cookie_len;
};
@@ -95,21 +97,29 @@ struct netlink_ext_ack {
#define NL_SET_ERR_MSG_MOD(extack, msg) \
NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
-#define NL_SET_BAD_ATTR(extack, attr) do { \
- if ((extack)) \
+#define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do { \
+ if ((extack)) { \
(extack)->bad_attr = (attr); \
+ (extack)->policy = (pol); \
+ } \
} while (0)
-#define NL_SET_ERR_MSG_ATTR(extack, attr, msg) do { \
- static const char __msg[] = msg; \
- struct netlink_ext_ack *__extack = (extack); \
- \
- if (__extack) { \
- __extack->_msg = __msg; \
- __extack->bad_attr = (attr); \
- } \
+#define NL_SET_BAD_ATTR(extack, attr) NL_SET_BAD_ATTR_POLICY(extack, attr, NULL)
+
+#define NL_SET_ERR_MSG_ATTR_POL(extack, attr, pol, msg) do { \
+ static const char __msg[] = msg; \
+ struct netlink_ext_ack *__extack = (extack); \
+ \
+ if (__extack) { \
+ __extack->_msg = __msg; \
+ __extack->bad_attr = (attr); \
+ __extack->policy = (pol); \
+ } \
} while (0)
+#define NL_SET_ERR_MSG_ATTR(extack, attr, msg) \
+ NL_SET_ERR_MSG_ATTR_POL(extack, attr, NULL, msg)
+
static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
u64 cookie)
{
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 5a5ff97cc596..6c9b08c0f071 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -1946,6 +1946,9 @@ int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state);
int netlink_policy_dump_write(struct sk_buff *skb,
struct netlink_policy_dump_state *state);
+int netlink_policy_dump_write_attr(struct sk_buff *skb,
+ const struct nla_policy *pt,
+ int nestattr);
void netlink_policy_dump_free(struct netlink_policy_dump_state *state);
#endif
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index eac8a6a648ea..b9c28c558698 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -129,6 +129,7 @@ struct nlmsgerr {
* @NLMSGERR_ATTR_COOKIE: arbitrary subsystem specific cookie to
* be used - in the success case - to identify a created
* object or operation or similar (binary)
+ * @NLMSGERR_ATTR_POLICY: policy for a rejected attribute
* @__NLMSGERR_ATTR_MAX: number of attributes
* @NLMSGERR_ATTR_MAX: highest attribute number
*/
@@ -137,6 +138,7 @@ enum nlmsgerr_attrs {
NLMSGERR_ATTR_MSG,
NLMSGERR_ATTR_OFFS,
NLMSGERR_ATTR_COOKIE,
+ NLMSGERR_ATTR_POLICY,
__NLMSGERR_ATTR_MAX,
NLMSGERR_ATTR_MAX = __NLMSGERR_ATTR_MAX - 1
diff --git a/lib/nlattr.c b/lib/nlattr.c
index 80ff9fe83696..cdd78c52c3c4 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -96,8 +96,8 @@ static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
continue;
if (nla_len(entry) < NLA_HDRLEN) {
- NL_SET_ERR_MSG_ATTR(extack, entry,
- "Array element too short");
+ NL_SET_ERR_MSG_ATTR_POL(extack, entry, policy,
+ "Array element too short");
return -ERANGE;
}
@@ -195,8 +195,8 @@ static int nla_validate_range_unsigned(const struct nla_policy *pt,
pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
current->comm, pt->type);
if (validate & NL_VALIDATE_STRICT_ATTRS) {
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "invalid attribute length");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "invalid attribute length");
return -EINVAL;
}
@@ -208,11 +208,11 @@ static int nla_validate_range_unsigned(const struct nla_policy *pt,
bool binary = pt->type == NLA_BINARY;
if (binary)
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "binary attribute size out of range");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "binary attribute size out of range");
else
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "integer out of range");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "integer out of range");
return -ERANGE;
}
@@ -291,8 +291,8 @@ static int nla_validate_int_range_signed(const struct nla_policy *pt,
nla_get_range_signed(pt, &range);
if (value < range.min || value > range.max) {
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "integer out of range");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "integer out of range");
return -ERANGE;
}
@@ -346,8 +346,8 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
current->comm, type);
if (validate & NL_VALIDATE_STRICT_ATTRS) {
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "invalid attribute length");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "invalid attribute length");
return -EINVAL;
}
}
@@ -355,14 +355,14 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
if (validate & NL_VALIDATE_NESTED) {
if ((pt->type == NLA_NESTED || pt->type == NLA_NESTED_ARRAY) &&
!(nla->nla_type & NLA_F_NESTED)) {
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "NLA_F_NESTED is missing");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "NLA_F_NESTED is missing");
return -EINVAL;
}
if (pt->type != NLA_NESTED && pt->type != NLA_NESTED_ARRAY &&
pt->type != NLA_UNSPEC && (nla->nla_type & NLA_F_NESTED)) {
- NL_SET_ERR_MSG_ATTR(extack, nla,
- "NLA_F_NESTED not expected");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "NLA_F_NESTED not expected");
return -EINVAL;
}
}
@@ -514,7 +514,8 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
return 0;
out_err:
- NL_SET_ERR_MSG_ATTR(extack, nla, "Attribute failed policy validation");
+ NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
+ "Attribute failed policy validation");
return err;
}
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index df675a8e1918..8273d5e70594 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2420,6 +2420,9 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
tlvlen += nla_total_size(sizeof(u32));
if (nlk_has_extack && extack && extack->cookie_len)
tlvlen += nla_total_size(extack->cookie_len);
+ /* the max policy content is currently ~44 bytes for range min/max */
+ if (err && nlk_has_extack && extack && extack->policy)
+ tlvlen += 64;
if (tlvlen)
flags |= NLM_F_ACK_TLVS;
@@ -2452,6 +2455,9 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
if (extack->cookie_len)
WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
extack->cookie_len, extack->cookie));
+ if (extack->policy)
+ netlink_policy_dump_write_attr(skb, extack->policy,
+ NLMSGERR_ATTR_POLICY);
}
nlmsg_end(skb, rep);
diff --git a/net/netlink/policy.c b/net/netlink/policy.c
index bb4e3ffb4924..b19f2a3f2533 100644
--- a/net/netlink/policy.c
+++ b/net/netlink/policy.c
@@ -332,6 +332,23 @@ __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
return -ENOBUFS;
}
+/**
+ * netlink_policy_dump_write_attr - write a given attribute policy
+ * @skb: the message skb to write to
+ * @pt: the attribute's policy
+ * @nestattr: the nested attribute ID to use
+ *
+ * Returns: 0 on success, an error code otherwise; -%ENODATA is
+ * special, indicating that there's no policy data and
+ * the attribute is generally rejected.
+ */
+int netlink_policy_dump_write_attr(struct sk_buff *skb,
+ const struct nla_policy *pt,
+ int nestattr)
+{
+ return __netlink_policy_dump_write_attr(NULL, skb, pt, nestattr);
+}
+
/**
* netlink_policy_dump_write - write current policy dump attributes
* @skb: the message skb to write to
--
2.26.2
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