2 files changed, 13 insertions, 2 deletions

diff --git a/include/net/netlink.h b/include/net/netlink.h
index 1f18b47f41b4..c77ed51c18f1 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -183,6 +183,7 @@ enum {
         NLA_REJECT,
         NLA_EXACT_LEN,
         NLA_EXACT_LEN_WARN,
+        NLA_MIN_LEN,
         __NLA_TYPE_MAX,
 };
 
@@ -212,6 +213,7 @@ enum nla_policy_validation {
  *    NLA_NUL_STRING       Maximum length of string (excluding NUL)
  *    NLA_FLAG             Unused
  *    NLA_BINARY           Maximum length of attribute payload
+ *    NLA_MIN_LEN          Minimum length of attribute payload
  *    NLA_NESTED,
  *    NLA_NESTED_ARRAY     Length verification is done by checking len of
  *                         nested header (or empty); len field is used if
@@ -230,6 +232,7 @@ enum nla_policy_validation {
  *                         it is rejected.
  *    NLA_EXACT_LEN_WARN   Attribute should have exactly this length, a warning
  *                         is logged if it is longer, shorter is rejected.
+ *    NLA_MIN_LEN          Minimum length of attribute payload
  *    All other            Minimum length of attribute payload
  *
  * Meaning of `validation_data' field:
@@ -281,7 +284,7 @@ enum nla_policy_validation {
  * static const struct nla_policy my_policy[ATTR_MAX+1] = {
  *      [ATTR_FOO] = { .type = NLA_U16 },
  *      [ATTR_BAR] = { .type = NLA_STRING, .len = BARSIZ },
- *      [ATTR_BAZ] = { .len = sizeof(struct mystruct) },
+ *      [ATTR_BAZ] = { .type = NLA_EXACT_LEN, .len = sizeof(struct mystruct) },
  *      [ATTR_GOO] = { .type = NLA_BITFIELD32, .validation_data = &myvalidflags },
  * };
  */
@@ -302,6 +305,7 @@ struct nla_policy {
 #define NLA_POLICY_EXACT_LEN(_len)      { .type = NLA_EXACT_LEN, .len = _len }
 #define NLA_POLICY_EXACT_LEN_WARN(_len) { .type = NLA_EXACT_LEN_WARN, \
                                           .len = _len }
+#define NLA_POLICY_MIN_LEN(_len)        { .type = NLA_MIN_LEN, .len = _len }
 
 #define NLA_POLICY_ETH_ADDR             NLA_POLICY_EXACT_LEN(ETH_ALEN)
 #define NLA_POLICY_ETH_ADDR_COMPAT      NLA_POLICY_EXACT_LEN_WARN(ETH_ALEN)
diff --git a/lib/nlattr.c b/lib/nlattr.c
index d26de6156b97..465c9e8ef8a5 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -278,10 +278,17 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
                         }
                 }
                 break;
+
+        case NLA_UNSPEC:
+        case NLA_MIN_LEN:
+                if (attrlen < pt->len)
+                        goto out_err;
+                break;
+
         default:
                 if (pt->len)
                         minlen = pt->len;
-                else if (pt->type != NLA_UNSPEC)
+                else
                         minlen = nla_attr_minlen[pt->type];
 
                 if (attrlen < minlen)