From: Matan Barak <matanb@xxxxxxxxxxxx>
When parsing netlink packets, users may want to do some extra
validations on the netlink attributes. Adding nla_parse_cb, which
gets an extra callback parameter. This function is invoked for every
netlink attribute. If the callback fails, parsing will fail as well.
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Matan Barak <matanb@xxxxxxxxxxxx>
Signed-off-by: Haggai Eran <haggaie@xxxxxxxxxxxx>
---
include/linux/netlink.h | 1 -
include/net/netlink.h | 5 +++++
lib/nlattr.c | 43 ++++++++++++++++++++++++++++++++++++++++---
3 files changed, 45 insertions(+), 4 deletions(-)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index da14ab6..a08b63b 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -117,7 +117,6 @@ netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
#define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
-
struct netlink_callback {
struct sk_buff *skb;
const struct nlmsghdr *nlh;
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 0e31727..70ba851 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -149,6 +149,8 @@
* nla_find() find attribute in stream of attributes
* nla_find_nested() find attribute in nested attributes
* nla_parse() parse and validate stream of attrs
+ * nla_parse_cb() parse stream of attrs and call to
+ * callback for every nlattr
* nla_parse_nested() parse nested attribuets
* nla_for_each_attr() loop over all attributes
* nla_for_each_nested() loop over the nested attributes
@@ -237,6 +239,9 @@ int nla_validate(const struct nlattr *head, int len, int maxtype,
const struct nla_policy *policy);
int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy);
+int nla_parse_cb(struct nlattr **tb, int maxtype, const struct nlattr *head,
+ int len, const struct nla_policy *policy,
+ int (*cb)(const struct nlattr *, void *), void *cb_priv);
int nla_policy_len(const struct nla_policy *, int);
struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype);
size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize);
diff --git a/lib/nlattr.c b/lib/nlattr.c
index f5907d2..ec79387 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -165,22 +165,28 @@ nla_policy_len(const struct nla_policy *p, int n)
EXPORT_SYMBOL(nla_policy_len);
/**
- * nla_parse - Parse a stream of attributes into a tb buffer
+ * nla_parse_cb - Parse a stream of attributes into a tb buffer with callback
* @tb: destination array with maxtype+1 elements
* @maxtype: maximum attribute type to be expected
* @head: head of attribute stream
* @len: length of attribute stream
* @policy: validation policy
+ * @cb: callback function and data, must not be NULL
+ * @cb_priv: private data for the callback
*
* Parses a stream of attributes and stores a pointer to each attribute in
* the tb array accessible via the attribute type. Attributes with a type
* exceeding maxtype will be silently ignored for backwards compatibility
* reasons. policy may be set to NULL if no validation is required.
+ * For every validated nla, the function calls the user-space callback.
+ * If the callback fails (returns with non-zero value), parsing is terminated
+ * and this value is returned as error.
*
* Returns 0 on success or a negative error code.
*/
-int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
- int len, const struct nla_policy *policy)
+int nla_parse_cb(struct nlattr **tb, int maxtype, const struct nlattr *head,
+ int len, const struct nla_policy *policy,
+ int (*cb)(const struct nlattr *, void *), void *cb_priv)
{
const struct nlattr *nla;
int rem, err;
@@ -196,6 +202,9 @@ int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
if (err < 0)
goto errout;
}
+ err = cb(nla, cb_priv);
+ if (err)
+ goto errout;
tb[type] = (struct nlattr *)nla;
}
@@ -209,6 +218,34 @@ int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
errout:
return err;
}
+EXPORT_SYMBOL(nla_parse_cb);
+
+static int nla_pass_all_cb(const struct nlattr *nla, void *priv)
+{
+ return 0;
+}
+
+/**
+ * nla_parse - Parse a stream of attributes into a tb buffer
+ * @tb: destination array with maxtype+1 elements
+ * @maxtype: maximum attribute type to be expected
+ * @head: head of attribute stream
+ * @len: length of attribute stream
+ * @policy: validation policy
+ *
+ * Parses a stream of attributes and stores a pointer to each attribute in
+ * the tb array accessible via the attribute type. Attributes with a type
+ * exceeding maxtype will be silently ignored for backwards compatibility
+ * reasons. policy may be set to NULL if no validation is required.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
+ int len, const struct nla_policy *policy)
+{
+ return nla_parse_cb(tb, maxtype, head, len, policy, nla_pass_all_cb,
+ NULL);
+}
EXPORT_SYMBOL(nla_parse);
/**
--
2.1.4
--
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