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, 31 insertions, 27 deletions

diff --git a/include/net/netlink.h b/include/net/netlink.h
index c0411f14fb53b..fdd317f8fde4b 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -181,8 +181,6 @@ enum {
 	NLA_S64,
 	NLA_BITFIELD32,
 	NLA_REJECT,
-	NLA_EXACT_LEN,
-	NLA_MIN_LEN,
 	__NLA_TYPE_MAX,
 };
 
@@ -199,11 +197,11 @@ struct netlink_range_validation_signed {
 enum nla_policy_validation {
 	NLA_VALIDATE_NONE,
 	NLA_VALIDATE_RANGE,
+	NLA_VALIDATE_RANGE_WARN_TOO_LONG,
 	NLA_VALIDATE_MIN,
 	NLA_VALIDATE_MAX,
 	NLA_VALIDATE_RANGE_PTR,
 	NLA_VALIDATE_FUNCTION,
-	NLA_VALIDATE_WARN_TOO_LONG,
 };
 
 /**
@@ -222,7 +220,7 @@ 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
+ *                         (but see also below with the validation type)
  *    NLA_NESTED,
  *    NLA_NESTED_ARRAY     Length verification is done by checking len of
  *                         nested header (or empty); len field is used if
@@ -237,11 +235,6 @@ enum nla_policy_validation {
  *                         just like "All other"
  *    NLA_BITFIELD32       Unused
  *    NLA_REJECT           Unused
- *    NLA_EXACT_LEN        Attribute should have exactly this length, otherwise
- *                         it is rejected or warned about, the latter happening
- *                         if and only if the `validation_type' is set to
- *                         NLA_VALIDATE_WARN_TOO_LONG.
- *    NLA_MIN_LEN          Minimum length of attribute payload
  *    All other            Minimum length of attribute payload
  *
  * Meaning of validation union:
@@ -296,6 +289,11 @@ enum nla_policy_validation {
  *                         pointer to a struct netlink_range_validation_signed
  *                         that indicates the min/max values.
  *                         Use NLA_POLICY_FULL_RANGE_SIGNED().
+ *
+ *    NLA_BINARY           If the validation type is like the ones for integers
+ *                         above, then the min/max length (not value like for
+ *                         integers) of the attribute is enforced.
+ *
  *    All other            Unused - but note that it's a union
  *
  * Meaning of `validate' field, use via NLA_POLICY_VALIDATE_FN:
@@ -309,7 +307,7 @@ 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] = { .type = NLA_EXACT_LEN, .len = sizeof(struct mystruct) },
+ *	[ATTR_BAZ] = NLA_POLICY_EXACT_LEN(sizeof(struct mystruct)),
  *	[ATTR_GOO] = NLA_POLICY_BITFIELD32(myvalidflags),
  * };
  */
@@ -335,9 +333,10 @@ struct nla_policy {
 		 * nesting validation starts here.
 		 *
 		 * Additionally, it means that NLA_UNSPEC is actually NLA_REJECT
-		 * for any types >= this, so need to use NLA_MIN_LEN to get the
-		 * previous pure { .len = xyz } behaviour. The advantage of this
-		 * is that types not specified in the policy will be rejected.
+		 * for any types >= this, so need to use NLA_POLICY_MIN_LEN() to
+		 * get the previous pure { .len = xyz } behaviour. The advantage
+		 * of this is that types not specified in the policy will be
+		 * rejected.
 		 *
 		 * For completely new families it should be set to 1 so that the
 		 * validation is enforced for all attributes. For existing ones
@@ -349,12 +348,6 @@ 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, .len = _len, \
-	  .validation_type = NLA_VALIDATE_WARN_TOO_LONG, }
-#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)
 
@@ -370,19 +363,21 @@ struct nla_policy {
 	{ .type = NLA_BITFIELD32, .bitfield32_valid = valid }
 
 #define __NLA_ENSURE(condition) BUILD_BUG_ON_ZERO(!(condition))
-#define NLA_ENSURE_UINT_TYPE(tp)			\
+#define NLA_ENSURE_UINT_OR_BINARY_TYPE(tp)		\
 	(__NLA_ENSURE(tp == NLA_U8 || tp == NLA_U16 ||	\
 		      tp == NLA_U32 || tp == NLA_U64 ||	\
-		      tp == NLA_MSECS) + tp)
+		      tp == NLA_MSECS ||		\
+		      tp == NLA_BINARY) + tp)
 #define NLA_ENSURE_SINT_TYPE(tp)			\
 	(__NLA_ENSURE(tp == NLA_S8 || tp == NLA_S16  ||	\
 		      tp == NLA_S32 || tp == NLA_S64) + tp)
-#define NLA_ENSURE_INT_TYPE(tp)				\
+#define NLA_ENSURE_INT_OR_BINARY_TYPE(tp)		\
 	(__NLA_ENSURE(tp == NLA_S8 || tp == NLA_U8 ||	\
 		      tp == NLA_S16 || tp == NLA_U16 ||	\
 		      tp == NLA_S32 || tp == NLA_U32 ||	\
 		      tp == NLA_S64 || tp == NLA_U64 ||	\
-		      tp == NLA_MSECS) + tp)
+		      tp == NLA_MSECS ||		\
+		      tp == NLA_BINARY) + tp)
 #define NLA_ENSURE_NO_VALIDATION_PTR(tp)		\
 	(__NLA_ENSURE(tp != NLA_BITFIELD32 &&		\
 		      tp != NLA_REJECT &&		\
@@ -390,14 +385,14 @@ struct nla_policy {
 		      tp != NLA_NESTED_ARRAY) + tp)
 
 #define NLA_POLICY_RANGE(tp, _min, _max) {		\
-	.type = NLA_ENSURE_INT_TYPE(tp),		\
+	.type = NLA_ENSURE_INT_OR_BINARY_TYPE(tp),	\
 	.validation_type = NLA_VALIDATE_RANGE,		\
 	.min = _min,					\
 	.max = _max					\
 }
 
 #define NLA_POLICY_FULL_RANGE(tp, _range) {		\
-	.type = NLA_ENSURE_UINT_TYPE(tp),		\
+	.type = NLA_ENSURE_UINT_OR_BINARY_TYPE(tp),	\
 	.validation_type = NLA_VALIDATE_RANGE_PTR,	\
 	.range = _range,				\
 }
@@ -409,13 +404,13 @@ struct nla_policy {
 }
 
 #define NLA_POLICY_MIN(tp, _min) {			\
-	.type = NLA_ENSURE_INT_TYPE(tp),		\
+	.type = NLA_ENSURE_INT_OR_BINARY_TYPE(tp),	\
 	.validation_type = NLA_VALIDATE_MIN,		\
 	.min = _min,					\
 }
 
 #define NLA_POLICY_MAX(tp, _max) {			\
-	.type = NLA_ENSURE_INT_TYPE(tp),		\
+	.type = NLA_ENSURE_INT_OR_BINARY_TYPE(tp),	\
 	.validation_type = NLA_VALIDATE_MAX,		\
 	.max = _max,					\
 }
@@ -427,6 +422,15 @@ struct nla_policy {
 	.len = __VA_ARGS__ + 0,				\
 }
 
+#define NLA_POLICY_EXACT_LEN(_len)	NLA_POLICY_RANGE(NLA_BINARY, _len, _len)
+#define NLA_POLICY_EXACT_LEN_WARN(_len) {			\
+	.type = NLA_BINARY,					\
+	.validation_type = NLA_VALIDATE_RANGE_WARN_TOO_LONG,	\
+	.min = _len,						\
+	.max = _len						\
+}
+#define NLA_POLICY_MIN_LEN(_len)	NLA_POLICY_MIN(NLA_BINARY, _len)
+
 /**
  * struct nl_info - netlink source information
  * @nlh: Netlink message header of original request