netlink: make NLA_BINARY validation more flexible

Add range validation for NLA_BINARY, allowing validation of any
combination of combination minimum or maximum lengths, using the
existing NLA_POLICY_RANGE()/NLA_POLICY_FULL_RANGE() macros, just
like for integers where the value is checked.

Also make NLA_POLICY_EXACT_LEN(), NLA_POLICY_EXACT_LEN_WARN()
and NLA_POLICY_MIN_LEN() special cases of this, removing the old
types NLA_EXACT_LEN and NLA_MIN_LEN.

This allows us to save some code where both minimum and maximum
lengths are requires, currently the policy only allows maximum
(NLA_BINARY), minimum (NLA_MIN_LEN) or exact (NLA_EXACT_LEN), so
a range of lengths cannot be accepted and must be checked by the
code that consumes the attributes later.

Also, this allows advertising the correct ranges in the policy
export to userspace. Here, NLA_MIN_LEN and NLA_EXACT_LEN already
were special cases of NLA_BINARY with min and min/max length
respectively.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 21 deletions

diff --git a/lib/nlattr.c b/lib/nlattr.c
index bc5b5cf608c4..665bdaff02c8 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -124,6 +124,7 @@ void nla_get_range_unsigned(const struct nla_policy *pt,
 		range->max = U8_MAX;
 		break;
 	case NLA_U16:
+	case NLA_BINARY:
 		range->max = U16_MAX;
 		break;
 	case NLA_U32:
@@ -140,6 +141,7 @@ void nla_get_range_unsigned(const struct nla_policy *pt,
 
 	switch (pt->validation_type) {
 	case NLA_VALIDATE_RANGE:
+	case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
 		range->min = pt->min;
 		range->max = pt->max;
 		break;
@@ -157,9 +159,10 @@ void nla_get_range_unsigned(const struct nla_policy *pt,
 	}
 }
 
-static int nla_validate_int_range_unsigned(const struct nla_policy *pt,
-					   const struct nlattr *nla,
-					   struct netlink_ext_ack *extack)
+static int nla_validate_range_unsigned(const struct nla_policy *pt,
+				       const struct nlattr *nla,
+				       struct netlink_ext_ack *extack,
+				       unsigned int validate)
 {
 	struct netlink_range_validation range;
 	u64 value;
@@ -178,15 +181,39 @@ static int nla_validate_int_range_unsigned(const struct nla_policy *pt,
 	case NLA_MSECS:
 		value = nla_get_u64(nla);
 		break;
+	case NLA_BINARY:
+		value = nla_len(nla);
+		break;
 	default:
 		return -EINVAL;
 	}
 
 	nla_get_range_unsigned(pt, &range);
 
+	if (pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG &&
+	    pt->type == NLA_BINARY && value > range.max) {
+		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");
+			return -EINVAL;
+		}
+
+		/* this assumes min <= max (don't validate against min) */
+		return 0;
+	}
+
 	if (value < range.min || value > range.max) {
-		NL_SET_ERR_MSG_ATTR(extack, nla,
-				    "integer out of range");
+		bool binary = pt->type == NLA_BINARY;
+
+		if (binary)
+			NL_SET_ERR_MSG_ATTR(extack, nla,
+					    "binary attribute size out of range");
+		else
+			NL_SET_ERR_MSG_ATTR(extack, nla,
+					    "integer out of range");
+
 		return -ERANGE;
 	}
 
@@ -274,7 +301,8 @@ static int nla_validate_int_range_signed(const struct nla_policy *pt,
 
 static int nla_validate_int_range(const struct nla_policy *pt,
 				  const struct nlattr *nla,
-				  struct netlink_ext_ack *extack)
+				  struct netlink_ext_ack *extack,
+				  unsigned int validate)
 {
 	switch (pt->type) {
 	case NLA_U8:
@@ -282,7 +310,8 @@ static int nla_validate_int_range(const struct nla_policy *pt,
 	case NLA_U32:
 	case NLA_U64:
 	case NLA_MSECS:
-		return nla_validate_int_range_unsigned(pt, nla, extack);
+	case NLA_BINARY:
+		return nla_validate_range_unsigned(pt, nla, extack, validate);
 	case NLA_S8:
 	case NLA_S16:
 	case NLA_S32:
@@ -313,10 +342,7 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 
 	BUG_ON(pt->type > NLA_TYPE_MAX);
 
-	if ((nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) ||
-	    (pt->type == NLA_EXACT_LEN &&
-	     pt->validation_type == NLA_VALIDATE_WARN_TOO_LONG &&
-	     attrlen != pt->len)) {
+	if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) {
 		pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
 				    current->comm, type);
 		if (validate & NL_VALIDATE_STRICT_ATTRS) {
@@ -449,19 +475,10 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 					    "Unsupported attribute");
 			return -EINVAL;
 		}
-		/* fall through */
-	case NLA_MIN_LEN:
 		if (attrlen < pt->len)
 			goto out_err;
 		break;
 
-	case NLA_EXACT_LEN:
-		if (pt->validation_type != NLA_VALIDATE_WARN_TOO_LONG) {
-			if (attrlen != pt->len)
-				goto out_err;
-			break;
-		}
-		/* fall through */
 	default:
 		if (pt->len)
 			minlen = pt->len;
@@ -479,9 +496,10 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 		break;
 	case NLA_VALIDATE_RANGE_PTR:
 	case NLA_VALIDATE_RANGE:
+	case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
 	case NLA_VALIDATE_MIN:
 	case NLA_VALIDATE_MAX:
-		err = nla_validate_int_range(pt, nla, extack);
+		err = nla_validate_int_range(pt, nla, extack, validate);
 		if (err)
 			return err;
 		break;